Switch to Hugo

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.

.github/CONTRIBUTING.md

@@ -142,7 +142,7 @@ and/or [`/bootstrap/js/src/`](https://github.com/twbs/bootstrap/tree/v4-dev/js/s
 
 Similarly, when contributing to Bootstrap's documentation, you should edit the
 documentation source files in
-[the `/bootstrap/site/docs/` directory of the `v4-dev` branch](https://github.com/twbs/bootstrap/tree/v4-dev/site/docs).
+[the `/bootstrap/site/content/docs/` directory of the `v4-dev` branch](https://github.com/twbs/bootstrap/tree/v4-dev/site/content/docs).
 **Do not edit the `gh-pages` branch.** That branch is generated from the
 documentation source files and is managed separately by the Bootstrap Core Team.
 

.github/workflows/docs.yml

@@ -9,7 +9,6 @@ on:
 env:
   CI: true
   NODE: 14.x
-  RUBY: 2.7.x
 
 jobs:
   docs:
@@ -24,25 +23,7 @@ jobs:
         with:
           node-version: "${{ env.NODE }}"
 
-      - name: Set up Ruby
-        uses: actions/setup-ruby@v1
-        with:
-          ruby-version: ${{ env.RUBY }}
-
-      - name: Set up Ruby env
-        run: |
-          echo "gem: --no-document" > ~/.gemrc # Disable gem docs
-          bundle config set clean 'true'
-          bundle config set deployment 'true'
-
-      - name: Set up Ruby cache
-        uses: actions/cache@v2
-        with:
-          path: vendor/bundle
-          key: ${{ runner.os }}-ruby-v${{ env.RUBY }}-${{ hashFiles('Gemfile') }}-${{ hashFiles('Gemfile.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-ruby-v${{ env.RUBY }}-${{ hashFiles('Gemfile') }}-${{ hashFiles('Gemfile.lock') }}
-            ${{ runner.os }}-ruby-v${{ env.RUBY }}-
+      - run: java -version
 
       - name: Set up npm cache
         uses: actions/cache@v2
@@ -53,19 +34,8 @@ jobs:
             ${{ runner.OS }}-node-v${{ env.NODE }}-${{ hashFiles('package.json') }}-${{ hashFiles('package-lock.json') }}
             ${{ runner.OS }}-node-v${{ env.NODE }}-
 
-      - run: ruby --version
-      - run: gem --version
-      - run: bundle --version
-      - run: java -version
-
       - name: Install npm dependencies
         run: npm ci
 
-      - name: Install bundler dependencies
-        run: bundle install --deployment --jobs=4 --retry=3 --clean
-
-      - name: Copy CSS and JS
-        run: npm run css-copy && npm run js-copy
-
       - name: Test docs
         run: npm run docs