Use the docs installation of the own repository

Author: ainagaya

.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 ".[docs]"
       - name: Sphinx build
         run: |
           cd docs && make html