Update docs.yml

Author: grimpirate

.github/workflows/docs.yml

@@ -19,6 +19,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: 3.x
+      - run: pip install 'mkdocstrings[python]'
       - run: pip install zensical
       - run: zensical build --clean 
       - uses: actions/upload-pages-artifact@v4