Update docs for new XXL grid tier

- Updates mentions of number and exact tiers
- Updates grid example to include xxl container
- Adds some scss-docs references
- Cleans up other grid mentions and docs
- Updates navbar example to include an expand at XXL variant

Clarify media query using .02px and bump from callout to warning

layout/z-index.md: retrieve z-index variables on build time

Update file size for the grid build

Rewrite grid docs to account for new grid tier

- Breaks grid content across multiple pages
- Updates mentions of grid tiers from five to six
- Rewrites how it works sections to reference new options and tiers

Move table of contents to new sidebar, restyle it to be simpler

Add an xxl grid tier

- Staring at my laptop, I realized I'm wasting away space. This adds a
significant amount of CSS, but it feels right already.
- Added the xxl tier with a width that divides by 12
- Motivation was originally trying to have a third column for our toc so
that our docs are more useful

Update devDependencies (#30544)

* @babel/plugin-proposal-object-rest-spread   ^7.9.0  →   ^7.9.5
* @babel/preset-env                           ^7.9.0  →   ^7.9.5
* @rollup/plugin-commonjs                    ^11.0.2  →  ^11.1.0
* @rollup/plugin-node-resolve                 ^7.1.1  →   ^7.1.3
* hugo-bin                                   ^0.56.3  →  ^0.57.0
* karma                                       ^4.4.1  →   ^5.0.1
* nodemon                                     ^2.0.2  →   ^2.0.3
* rollup                                      ^2.3.3  →   ^2.6.1
* stylelint                                  ^13.3.0  →  ^13.3.2
* terser                                     ^4.6.10  →  ^4.6.11

Use `box-shadow` mixin for `.btn` (#30512)

Co-authored-by: Martijn Cuppens <martijn.cuppens@gmail.com>

Use `box-shadow` mixin for `.form-select` (#30555)

Use custom properties for font-stacks (#30509)

Remove redundant class and line height (#30542)

Pass multiple classes to `classList.add` / `classList.remove` (#30537)

This is supported by our currently supported browsers.

Add v4-dev in bundlewatch config. (#30541)

Add checkbox transition (#30528)

Replace bundlesize with bundlewatch. (#30538)

Fix spinner-grow animation (#30504)

* Fix spinner-grow animation

Safari seems to be interpreting the old keyframes animation as incomplete. Adding `transform` to the second frame seems to resolve the issue.

Co-Authored-By: Martijn Cuppens <martijn.cuppens@gmail.com>

Use correct hex color code(#30533)

Bump autoprefixer from 9.7.5 to 9.7.6 (#30524)

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 9.7.5 to 9.7.6.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/9.7.5...9.7.6)

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Bump rollup from 2.3.2 to 2.3.3 (#30523)

Bumps [rollup](https://github.com/rollup/rollup) from 2.3.2 to 2.3.3.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v2.3.2...v2.3.3)

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Bump stylelint from 13.2.1 to 13.3.0 (#30522)

Bumps [stylelint](https://github.com/stylelint/stylelint) from 13.2.1 to 13.3.0.
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/master/CHANGELOG.md)
- [Commits](https://github.com/stylelint/stylelint/compare/13.2.1...13.3.0)

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Create `scss-docs` shortcode to get some snippets from the Scs… (#30502)

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

Add `.card-footer` color (#30515)

Add nav link transition (#29988)

Update devDependencies and regenerate package-lock.json (#30501)

* linkinator 2.0.6
* rollup 2.3.2
* terser 4.6.10

We are now down to one low npm vulnerability

Fix card list group borders & radii (#30497)

Use `box-shadow` mixin for form controls (#30480)

Always modal scroll top to 0

Fix border radii

Fix CSS and improve docs

Add Full-Screen size to Modal and Responsive variations for breakpoints
(Works from breakpoint and down)

transition() mixin prevent redundant 'transition: none' and pass `null` (#30391)

* Prevent redundant 'none' for prefers-reduced-motion

* Output warning when use 'none' or 'null' with multiple arguments

* Fix for libsass(node-sass)

Fix date inputs heights in safari

Fix active state dropdown

Use unordered lists in dropdown-menus

Docs: Use unordered lists in dropdowns

Fix text decorations (#30492)

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

Require `.form-label` classes on form labels (#30476)

docs(tables): 1, 2, 2, 4… (#30489)

Co-authored-by: XhmikosR <xhmikosr@gmail.com>

Regenerate package-lock.json. (#30488)

We are down to 2 npm vulnerabilities (1 low, 1 high).

Bump eslint-plugin-import from 2.20.1 to 2.20.2 (#30486)

Bumps [eslint-plugin-import](https://github.com/benmosher/eslint-plugin-import) from 2.20.1 to 2.20.2.
- [Release notes](https://github.com/benmosher/eslint-plugin-import/releases)
- [Changelog](https://github.com/benmosher/eslint-plugin-import/blob/master/CHANGELOG.md)
- [Commits](https://github.com/benmosher/eslint-plugin-import/compare/v2.20.1...v2.20.2)

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Bump rollup from 2.2.0 to 2.3.1 (#30485)

Bumps [rollup](https://github.com/rollup/rollup) from 2.2.0 to 2.3.1.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v2.2.0...v2.3.1)

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Bump terser from 4.6.7 to 4.6.9 (#30483)

Bumps [terser](https://github.com/terser/terser) from 4.6.7 to 4.6.9.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/compare/v4.6.7...v4.6.9)

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Bump eslint-plugin-unicorn from 18.0.0 to 18.0.1 (#30484)

Bumps [eslint-plugin-unicorn](https://github.com/sindresorhus/eslint-plugin-unicorn) from 18.0.0 to 18.0.1.
- [Release notes](https://github.com/sindresorhus/eslint-plugin-unicorn/releases)
- [Commits](https://github.com/sindresorhus/eslint-plugin-unicorn/compare/v18.0.0...v18.0.1)

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Use variables for list-group-item color levels (#30009)

Co-authored-by: Martijn Cuppens <martijn.cuppens@gmail.com>

Cleanup responsive tables (#30482)

Switch to custom properties to control grid gutter widths (#30475)

Remove `MSPointerEvent` and `ms-touch-action` in tests (#30463)

Use `textContent` instead of `innerText`. (#30462)

It's supported by all of our supported browsers.

Order sizes variables (#30479)

docs: remove `makeArray` (#30470)

Simplify sidebar styles

docs(sidenav): use class selector for active item

docs(sidenav): transition arrow too

docs(sidenav): get rid of custom JS for active state

docs(sidenav): fix struggling CSS when collapsing sidenav

docs(sidenav): use collapse components

Dist (#29924)

Remove holder.js leftovers (#30469)

docs: remove duplicate code for indeterminate (#30471)

v5 tabs - accessibility issue when using ul/li semantic

Add aria-role presentation on li element when ul element has role tablist and remove dropdown from visual tests as they've been removed from doc

Update eslint-plugin-unicorn to v18.0.0 (#30461)

.gitignore: add Jekyll's cache folder (#30454)

So that when we switch branches the folder is ignored.

Regenerate package-lock.json to fix npm vulnerabilities (#30425)

3 left, 2 low and 1 high

Bump karma-rollup-preprocessor from 7.0.4 to 7.0.5 (#30459)

Bumps [karma-rollup-preprocessor](https://github.com/jlmakes/karma-rollup-preprocessor) from 7.0.4 to 7.0.5.
- [Release notes](https://github.com/jlmakes/karma-rollup-preprocessor/releases)
- [Changelog](https://github.com/jlmakes/karma-rollup-preprocessor/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jlmakes/karma-rollup-preprocessor/compare/7.0.4...7.0.5)

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Bump rollup from 2.1.0 to 2.2.0 (#30458)

Bumps [rollup](https://github.com/rollup/rollup) from 2.1.0 to 2.2.0.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v2.1.0...v2.2.0)

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Bump karma-jasmine-html-reporter from 1.5.2 to 1.5.3 (#30457)

Bumps [karma-jasmine-html-reporter](https://github.com/dfederm/karma-jasmine-html-reporter) from 1.5.2 to 1.5.3.
- [Release notes](https://github.com/dfederm/karma-jasmine-html-reporter/releases)
- [Commits](https://github.com/dfederm/karma-jasmine-html-reporter/compare/v1.5.2...v1.5.3)

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Bump lockfile-lint from 4.2.1 to 4.2.2 (#30456)

Bumps [lockfile-lint](https://github.com/lirantal/lockfile-lint) from 4.2.1 to 4.2.2.
- [Release notes](https://github.com/lirantal/lockfile-lint/releases)
- [Commits](https://github.com/lirantal/lockfile-lint/compare/lockfile-lint@4.2.1...lockfile-lint@4.2.2)

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fix babel config in our files

Adapt rollup config for recent `@babel/present-env` version

Bump @babel/preset-env from 7.8.7 to 7.9.0

Bumps [@babel/preset-env](https://github.com/babel/babel) from 7.8.7 to 7.9.0.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.8.7...v7.9.0)

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fix: remove make array util function (#30430)

Fix redirected links.

Fix links after #30041

Bump hugo-bin from 0.55.1 to 0.56.3 (#30446)

Bumps [hugo-bin](https://github.com/fenneclab/hugo-bin) from 0.55.1 to 0.56.3.
- [Release notes](https://github.com/fenneclab/hugo-bin/releases)
- [Commits](https://github.com/fenneclab/hugo-bin/compare/v0.55.1...v0.56.3)

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Bump karma-rollup-preprocessor from 7.0.3 to 7.0.4 (#30445)

Bumps [karma-rollup-preprocessor](https://github.com/jlmakes/karma-rollup-preprocessor) from 7.0.3 to 7.0.4.
- [Release notes](https://github.com/jlmakes/karma-rollup-preprocessor/releases)
- [Changelog](https://github.com/jlmakes/karma-rollup-preprocessor/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jlmakes/karma-rollup-preprocessor/compare/7.0.3...7.0.4)

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Bump @babel/plugin-proposal-object-rest-spread from 7.8.3 to 7.9.0 (#30444)

Bumps [@babel/plugin-proposal-object-rest-spread](https://github.com/babel/babel) from 7.8.3 to 7.9.0.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.8.3...v7.9.0)

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Bump @babel/core from 7.8.7 to 7.9.0 (#30443)

Bumps [@babel/core](https://github.com/babel/babel) from 7.8.7 to 7.9.0.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.8.7...v7.9.0)

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Bump autoprefixer from 9.7.4 to 9.7.5 (#30442)

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 9.7.4 to 9.7.5.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/9.7.4...9.7.5)

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Bump lockfile-lint from 4.1.0 to 4.2.1 (#30441)

Bumps [lockfile-lint](https://github.com/lirantal/lockfile-lint) from 4.1.0 to 4.2.1.
- [Release notes](https://github.com/lirantal/lockfile-lint/releases)
- [Commits](https://github.com/lirantal/lockfile-lint/compare/lockfile-lint@4.1.0...lockfile-lint@4.2.1)

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Add accessible name to fieldset

Add explicit aria-label to unlabeled controls

- in particular, controls that just relied on `placeholder`, as this is still not officially/consistently supported as a valid way to provide an accessible name (though some browsers do use it as a fallback)

Remove unnecessary <form> elements, add a submit button to validation example

Add explicit title to iframe embed

Add explicit scope="col" to <th> column headers

Add `.caption-top` for tables (#30435)

* Move caption-side to <table> element in Reboot

* Add class for .caption-top

File chooser size (#30040)

Co-authored-by: David Van Doninck <david.vandoninck@intracto.com>
Co-authored-by: XhmikosR <xhmikosr@gmail.com>
Co-authored-by: Martijn Cuppens <martijn.cuppens@gmail.com>

Make form-check label customizable (#30426)

Co-authored-by: Martijn Cuppens <martijn.cuppens@gmail.com>

Update modal docs (#30325)

Added focus state to .btn-link (#30036)

Use WCAG contrast algo (#30168)

Use next dropdown menu instead of first of the parent

Simplify input groups by dropping `.input-group-prepend` and `.input-group-append`

Documentation skip links (#30073)

* docs(skip-links): add a skip to main navigation skip link

* docs(skip-links): revamp skip-links pattern

* docs(navs): use aria-label on navs

* docs(navs): use 'docs navigation' label in sidebar nav

Use a link helper instead of the text color utility

Fix wrapping bug (#30345)

Merge pull request #30389 from twbs/underline-links

v5: Underline links

Merge branch 'master' into underline-links

Remove redundant text decoration from hover states

Restore hover text decoration on toc links