Test doc builds in CI

.github/workflows/ci.yaml

@@ -32,3 +32,22 @@ jobs:
 
       - name: Run tests
         run: python -m tox -e py -- --verbose
+
+  docs:
+    # Test documentation builds.
+    # This environment mirrors the ReadTheDocs build environment.
+    name: Docs
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python }}
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.12"
+
+      - name: Install tox
+        run: python -m pip install tox
+
+      - name: Run tests
+        run: python -m tox -e docs