Imgui examples.

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 https://github.com/ocornut/imgui/issues/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.