Update documentation.yml

.github/workflows/documentation.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/setup-python@v5
       - name: Install dependencies
         run: |
-          pip install sphinx sphinx_rtd_theme myst_parser
+          pip install sphinx sphinx_rtd_theme myst_parser numpydoc
       - name: Sphinx build
         run: |
           sphinx-build -b html ./ _build/