* Backport #32037
Add `.navbar-nav-scroll` for vertical scrolling of navbar content
* drop the css var for a Sass css
Co-authored-by: Mark Otto <markdotto@gmail.com>
This commit includes all the needed workarounds and most changes from the main branch for everything to work, like:
* removing empty lines in raw HTML that break output
* read .browserslistrc, CSS variables from disk instead of duplicating it
* using Hugo mounts
* using Hugo for the docs CSS/JS
* move ToC Sass code to a separate file while adapting it for Hugo
Thus, this patch makes our npm scripts faster since lint runs on one step and there's no separate docs assets processing.
