Speed up CI and test in a matrix of Node 20–25

.github/workflows/build-test.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        node: [20, 22, 24, 25]
+    steps:
+      - uses: actions/checkout@v6
+      - uses: actions/setup-node@v6
+        id: node
+        with:
+          node-version: ${{ matrix.node }}
+          cache: npm
+      - name: "Install, lint and build production outputs (Node ${{ steps.node.outputs.node-version }})"
+        run: |
+          npm run build-package
+      - name: "Build development outputs and (Xvfb) run JS tests in Firefox & Chrome"
+        run: |
+          firefox --version
+          google-chrome --version
+          xvfb-run npm test

README.md

@@ -148,6 +148,11 @@ should also be updated so the documentation site matches the NPM package feature
 2. Make sure your local `main` branch is up to date.
 3. Push the `main` branch to the `prod` branch: `git push origin main:prod`.
 
+_(The same is triggered by submitting a new GitHub Release, so the steps above can be
+skipped if you plan to publish a GitHub Release for the version tag — which you should.
+In such case the site deployment will be taken care of by automation, publishing the
+reference the release tag actually points to.)_
+
 A notice will be posted in #www-notify on Slack when the push has completed.
 
 ### Pushing to demo