closes #780

Got the basics working for an examples app. A selector list of examples on the right (just globs everything), displays the source of the selected example on the right and it is editable, and the example can be run (just POpen using the current source text).

todo:

• decide how to ship and have it fetchable via uv
• syntax highlighting would be nice, ImGuiColorTextEdit seems like it's not maintained anymore and I could get the example in imgui-bundle to run, I was able to run the imgui_md example from imgui-bundle but can't figure out how to just get the markdown text editor and put it in my window here. @panxinmiao @FlynnOConnell have you used imgui for syntax highlighting by any chance?