GUI app with nim

[jmgomez]

Yes, it support Linux as a target. Also Android and iOS. NimForUE however dont, 
although it's only required for dev. You can only dev in Win or MacOS (more 
involved) since it supports Mac which uses Clang, shouldnt be too difficult to 
port to Lin. I can help/guide if someone wants to PR Lin support but I dont 
have plans to add it myself in the short term