ci: build, render and deploy the roadmap explorer

Run the tests, assemble the site with build revision info, render the
PDF and PNG, deploy to GitHub Pages from master and attach the PDF and
PNG to published releases.

.github/workflows/pages.yml

@@ -0,0 +1,104 @@
+name: Roadmap explorer
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - README.md
+      - "site/**"
+      - .github/workflows/pages.yml
+  pull_request:
+    paths:
+      - README.md
+      - "site/**"
+      - .github/workflows/pages.yml
+  release:
+    types: [published]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Test and build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Test the README parser and map layout
+        run: node --test site/parser.test.mjs
+
+      - name: Assemble the site
+        run: |
+          mkdir _site
+          cp site/*.html site/*.css site/*.js site/map.json README.md _site/
+          cp -r site/fonts site/assets _site/
+          # Revision shown in the credits: the release tag, or tag-commits-hash between releases.
+          VERSION="$(git describe --tags --always)" DATE="$(git log -1 --format=%cs)" \
+            node -e 'console.log(JSON.stringify({ version: process.env.VERSION, date: process.env.DATE }))' > _site/build.json
+          cat _site/build.json
+
+      - name: Install Chromium
+        run: |
+          npm install --no-save --no-package-lock playwright@1
+          npx playwright install --with-deps chromium
+
+      - name: Render the roadmap to PDF and PNG
+        run: node site/tools/render.mjs _site / _site
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: roadmap-render
+          path: |
+            _site/Embedded-Engineering-Roadmap.pdf
+            _site/Embedded-Engineering-Roadmap.png
+          if-no-files-found: error
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: _site
+
+  deploy:
+    name: Deploy to GitHub Pages
+    if: github.event_name != 'pull_request' && github.ref == 'refs/heads/master'
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      pages: write
+      id-token: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@v4
+
+  release-assets:
+    name: Attach PDF and PNG to the release
+    if: github.event_name == 'release'
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: roadmap-render
+
+      - name: Upload release assets
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+          TAG: ${{ github.event.release.tag_name }}
+        run: gh release upload "$TAG" Embedded-Engineering-Roadmap.pdf Embedded-Engineering-Roadmap.png --clobber