put fail on warning for the documentation workflow

Author: rocco8773

.github/workflows/documentation.yml

@@ -40,7 +40,7 @@ jobs:
         sudo apt-get install graphviz pandoc
     - name: Build Docs
       run: |
-        sphinx-build ./docs ./docs/_build -n --keep-going -b html -q
+        sphinx-build ./docs ./docs/_build -n --keep-going -W -b html -q
 
   sphinx_limits:
     name: Doc Build on ${{ matrix.sphinx }}