slimgui: Updated ImGui bindings for Python

Work in progress Dear ImGui bindings for Python.

Motivation:

• Modernized build process to support Python typings (.pyi files) to allow good IDE support (auto-complete, type checking in VSCode)
• Closely match the Dear ImGui API but adapt for Python as necessary. Don't invent new API concepts.

Very similar to https://github.com/pyimgui/pyimgui except built with Nanobind to better support typings.

Development

python3 -m venv .venv
.venv\Scripts\activate.bat
pip install git+https://github.com/wjakob/nanobind scikit-build-core[pyproject] click glfw pyopengl numpy
pip install --no-build-isolation -ve .
python gen\gen_nb.py > src\im_enums.inl

Cimgui outputs for some API generation

Switch to v1.90.5 branch for imgui before running generator.bat.