ci: add stubs generation on Windows

Author: jcarpent

.github/workflows/windows-conda.yml

@@ -47,6 +47,10 @@ jobs:
         :: Build and Install
         cmake --build . --config Release --target install
 
+        :: Build stubs
+        git clone https://github.com/jcarpent/pybind11-stubgen.git
+        python "%CD%\pybind11-stubgen\pybind11_stubgen\__init__.py" -o %CONDA_PREFIX%\Lib\site-packages\eigenpy eigenpy --boost-python --ignore-invalid signature --no-setup-py --root-module-suffix ""
+
         :: Testing
         ctest --output-on-failure -C Release -V