* @babel/core                      ^7.15.5  →   ^7.15.8
* @babel/preset-env                ^7.15.6  →   ^7.15.8
* @rollup/plugin-commonjs          ^20.0.0  →   ^21.0.1
* @rollup/plugin-node-resolve      ^13.0.5  →   ^13.0.6
* autoprefixer                     ^10.3.6  →   ^10.3.7
* babel-plugin-istanbul             ^6.0.0  →    ^6.1.1
* clean-css-cli                     ^5.3.3  →    ^5.4.2
* eslint                           ^7.32.0  →    ^8.0.0
* eslint-config-xo                 ^0.38.0  →   ^0.39.0
* eslint-plugin-import             ^2.24.2  →   ^2.25.1
* eslint-plugin-qunit               ^6.2.0  →    ^7.0.0
* eslint-plugin-unicorn            ^36.0.0  →   ^37.0.1
* karma                             ^6.3.4  →    ^6.3.5
* linkinator                       ^2.14.0  →   ^2.14.4
* nodemon                          ^2.0.13  →   ^2.0.14
* postcss                           ^8.3.8  →   ^8.3.11
* postcss-cli                       ^9.0.0  →    ^9.0.1
* rollup                           ^2.57.0  →   ^2.58.0
* stylelint-config-twbs-bootstrap   ^2.2.3  →    ^2.2.4
* vnu-jar                           21.9.2  →  21.10.12

This is so that it's consistent with the JS workflow thus the cache should match.

* lowercase `runner.os`
* remove `CI` environment variable since it's already set by the runner

This should show any colors in the output

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.

Also, reword Node.js setup step