ci: add check for sphinx autodocs

Fix eclipse-basyx#115

.github/workflows/ci.yml

@@ -89,6 +89,24 @@ jobs:
       run: |
         codeblocks python README.md | python
 
+  docs:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ env.X_PYTHON_VERSION }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ env.X_PYTHON_VERSION }}
+    - name: Install Python dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+        pip install -r docs/add-requirements.txt
+    - name: Check documentation for errors
+      run: |
+        SPHINXOPTS="-a -E -n -W --keep-going" make -C docs html
+
   package:
     runs-on: ubuntu-latest