Debug aframe template

[chrislatorres]

Currently getting: TypeError: navigator.xr.requestDevice is not a function

Template is: https://github.com/exokitxr/studio/blob/master/aframe.html

[avaer]

This is a symptom of A-Frame not supporting the current WebXR spec. Until that's updated (most likely through THREE.js), we could make the iframe load in WebVR mode, if it's detected it's a-frame. We will need this kind of detection anyway for opening the editors.

I don't think we actually can back-poly this old API in Exokit, because doing so is detected by expecters of the new API (such as WebXR samples) to start polyfilling everything.