feat: add button to create empty app in scene inspector (global apps list)

[wyattlovesgrapes]

Issue

For things like skybox, UI panels, global event listeners users may not want them attached to physical glb's in their world right now. While in one sense this isn't limiting as you could just hide these functions on any model in your game world, a graceful solution could be adding a button to the scene inspector (global apps list) which allows you to create empty apps which you can open and script from the inspector.

Solution