WebXR support

[Squareys]

Hi @buesing !

Quite a while ago we had a quick exchange about getting "Konterball" onto Construct Arcade. Now I finally had the time to contribute the WebXR support, which seemed to only require an upgrade of the Three.js library!

This version was tested on the Oculus Quest, and while it only uses the Gaze-controls, works great and is fun!

Best, Jonathan