Vendor the JavaScript library dependencies

Use NPM to manage their versions: manually vendoring the libraries isn't feasible for Octokit, as its libraries aren't provided as single-file imports, and have nested dependencies of their own. Since NPM is needed to resolve that, use it for the other dependencies too.

Hugo's built-in bundling and minification support is used, though it means that the dependencies are duplicated within the scripts imported on different pages. I think that could be avoided by introducing a middle layer of JS assets that bundle the dependencies but aren't bundled themselves.

.github/workflows/hugo.yml

@@ -47,6 +47,9 @@ jobs:
         id: pages
         uses: actions/configure-pages@v5
 
+      - name: Install Node.js dependencies
+        run: npm ci
+
       - name: Build with Hugo
         env:
           HUGO_CACHEDIR: ${{ runner.temp }}/hugo_cache