Hexa.ImGui update tracking requirements for 2.1.2

[Doprez]

https://github.com/HexaEngine/Hexa.NET.ImGui/releases/tag/2.1.2

I can take a look at this when I have some time but the ImGui library had some updates that I would like to test out. Based on the release features I am hoping to see if the clipboard function make a bit more sense and maybe implement them if so.

possibly breaking changes to the ImageButton()? Based on how we are using it though maybe we can get around ImGui worst case.

parameter name changes to BeginChild()

I think those are the only things we are using that would or could break so it should be fairly simple.