ci: check for warnings when rendering documentation

.github/workflows/docs.yaml

@@ -0,0 +1,22 @@
+name: Documentation
+
+on:
+  push:
+    paths:
+      - 'Documentation/**'
+  pull_request:
+    paths:
+      - 'Documentation/**'
+
+jobs:
+  tests:
+    name: Rendering
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Documentation renders without warnings
+        run: |
+          docker run --rm --pull always -v $(pwd):/project \
+             ghcr.io/typo3-documentation/render-guides:latest --config=Documentation --no-progress --fail-on-log