init submodules

Author: Nicolas Béreux

.github/workflows/docs.yaml

@@ -13,6 +13,9 @@ jobs:
       - uses: actions/setup-python@v5
         with: 
           python-version: 3.12
+      - name: init submodule
+        run:
+	  git submodule update --init --recursive
       - name: Install dependencies
         run: |
           pip install sphinx sphinx_rtd_theme myst_parser sphinxcontrib-bibtex sphinx-gallery matplotlib