add ipython to docs workflow

.github/workflows/builddocs.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Install dependencies
         run: |
           sudo apt-get install -y pandoc
-          pip install sphinx sphinx_rtd_theme myst_parser furo nbsphinx scikit-fmm
+          pip install sphinx sphinx_rtd_theme myst_parser furo nbsphinx scikit-fmm ipython
           pip install -r requirements.txt
       - name: Sphinx build
         run: |