Install mkdocstrings in Zensical workflow

Author: Electronic-Mango

.github/workflows/docs.yml

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