Update devDependencies

Update devDependencies

* @babel/cli                   ^7.12.13  →  ^7.12.16
* @babel/core                  ^7.12.13  →  ^7.12.16
* @babel/preset-env            ^7.12.13  →  ^7.12.16
* @rollup/plugin-babel           ^5.2.3  →    ^5.3.0
* @rollup/plugin-node-resolve   ^11.1.1  →   ^11.2.0
* eslint                        ^7.19.0  →   ^7.20.0
* eslint-plugin-unicorn         ^27.0.0  →   ^28.0.1
* karma                          ^6.0.4  →    ^6.1.1
* postcss                        ^8.2.5  →    ^8.2.6
* rollup                        ^2.38.5  →   ^2.39.0
* stylelint                     ^13.9.0  →  ^13.10.0

Kept clean-css-cli to 4.x for the time being.