Example: `imgui`

[dschrempf]

This is another example we could try:

• https://github.com/ocornut/imgui using the C interface https://github.com/cimgui/cimgui
• https://github.com/epezent/implot using the C interface https://github.com/cimgui/cimplot

I played around a bit but the libraries are quite hard to compile (they do not use pkg-config).