Merge branch 'v4-dev' into v4-docs-streamlined

diff --cc docs/_includes/footer.html
Simple merge

diff --cc docs/_includes/nav-home.html
Simple merge

diff --cc docs/assets/scss/_content.scss
Simple merge

diff --cc docs/assets/scss/_masthead.scss
Simple merge

diff --cc docs/getting-started/download.md
Simple merge

diff --cc docs/getting-started/introduction.md
Simple merge

diff --cc docs/migration.md
Simple merge