CI: enable strict mode for mkdocs build to avoid deadlinks (#377)

Author: Horgix

.github/workflows/build-docs.yaml

@@ -27,4 +27,4 @@ jobs:
           restore-keys: |
             mkdocs-material-
       - run: pip install -r requirements.txt
-      - run: mkdocs gh-deploy --force
+      - run: mkdocs gh-deploy --force --strict