Add missing type stubs.

.github/workflows/python-package.yml

@@ -29,7 +29,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install flake8 check-manifest pytest codecov coverage mypy
+        python -m pip install flake8 check-manifest pytest codecov coverage mypy types-setuptools types-docutils
         python -m pip install ${{ matrix.pip-sphinx }}
         pip install .
     - name: Check manifest