Test the documentation builds in CI

.github/workflows/tests.yml

@@ -11,6 +11,7 @@ on:
       - "setup.*"
       - "src/**/*"
       - "tests/*.py"
+      - "docs/**/*"
 
 jobs:
   lint:
@@ -56,3 +57,20 @@ jobs:
         run: python -m pip install tox
       - name: Test
         run: python -m tox -e py
+
+  docs:
+    name: Test documentation builds
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.inputs.branch }}
+      - name: Use Python 3.10
+        uses: actions/setup-python@v2
+        with:
+          python-version: "3.10"
+      - name: Install test dependencies
+        run: python -m pip install tox
+      - name: Test
+        run: python -m tox -e docs