ci: install venv-pins-python ipython kernel for docs

Author: machow

.github/workflows/ci.yml

@@ -69,6 +69,7 @@ jobs:
           python -m pip install --upgrade pip
           python -m pip install -r requirements/dev.txt
           python -m pip install -e .
+          ipython kernel install --name "venv-pins-python" --user
       - uses: r-lib/actions/setup-pandoc@v1
         with:
           pandoc-version: '2.17.0.1'