Imgui examples.

[Sebanisu]

Imgui and Imgui with docking is in Conan. We could add a small example project using opengl for people to try. I started with an older version of this project that had sfml and imgui. I see that is removed now. I think unless I get busy I'll try to make something and create a pull request.
If you guys think this is a good or bad idea let me know.
https://conan.io/center/imgui
imgui/cci.20220207+1.87.docking
imgui/1.87
ocornut/imgui#2109
The docking branch adds alot of nice features to imgui like multiple windows that can be dragged in and out of the main window and be docked multiple ways.