CI: check for broken links on website

Ensure all internal links on our website are working.

External links are not checked to avoid flakiness.

Author: strager

.github/docker/Dockerfile

@@ -62,6 +62,7 @@ RUN \
       ninja-build \
       nodejs \
       python3.7 \
+      python3.7-venv \
       sudo \
       tar \
       unzip \

.github/workflows/build-website.yml

@@ -11,7 +11,7 @@ jobs:
   build:
     name: website
     runs-on: ubuntu-latest
-    container: ghcr.io/quick-lint/quick-lint-js-github-builder:v1
+    container: ghcr.io/quick-lint/quick-lint-js-github-builder:v3
     env:
       QLJS_COLLECT_COPYRIGHT_NO_WARNINGS: 1
     steps:
@@ -40,6 +40,29 @@ jobs:
       - name: bundle site
         run: cd website && zip -r ../website.zip www
 
+      - name: set up check-links
+        run: |
+          python3.7 -m venv ENV
+          ENV/bin/pip install bs4 requests
+      - name: check links (dev)
+        run: |
+          cd website/
+          yarn start localhost 9001 &
+          sleep 0.5  # HACK(strager): Wait for server to start.
+          cd ../
+          ./ENV/bin/python ./tools/check-links http://localhost:9001/
+          kill %1
+        shell: bash
+      - name: check links (build)
+        run: |
+          cd website/www/
+          python3.7 -m http.server 9002 &
+          sleep 0.5  # HACK(strager): Wait for server to start.
+          cd ../../
+          ./ENV/bin/python ./tools/check-links http://localhost:9002/
+          kill %1
+        shell: bash
+
       - name: upload build to workflow
         uses: actions/upload-artifact@v2
         with: