webxr

See:
https://forum.babylonjs.com/t/can-gltf-export-a-specific-mesh-from-scene/10641/3

Repro:
https://www.babylonjs-playground.com/#YBEKDT#4

Expected result:
Fan materials and textures should not be included in exported glTF from this playground.

Running the tabs default launch command (-t) does not respect redirects at the target.

$ node . -t https://aframe.io/a-painter

☝️ The above will error, even though the server will redirect to https://aframe.io/a-painter/ and serve HTML there:

$ curl -i https://aframe.io/a-painter
HTTP/1.1 301 Moved Permanently
Date: Mon, 03 Jun 2019 20:10:27 GMT
Content-Type: text/ht

You should be able to add text to a scene. Either as a Text Geometry or SDF text, probably both.

There's already a text component in AFrame that we can use in Hubs. We would need to add a new Spoke node with the ability to preview the text.

I think we should export the following properties:

value
align
anchor
baseline
color
he

Noticed the right half of the keyboard works correctly for transparency during hover, but the left side keys show a black background on hover. The keys circled below are the ones tested as having this issue.

![moonkeyboard](https://user-images.githubuserco

Ideally we will have a gltf for each device, but in the meantime we could use a generic VR input device like https://poly.google.com/view/cUT5C1Krx7g or https://poly.google.com/view/0n5B6e5lYZe

Freeze background (or fallback) checkbox is for low-spec devices or if it's generally distracting. This checkbox should be added to the lower right corner.

if user visits location that does not exists he sees message that can be closed or timed out in 10 seconds that leaves user on what looks like loading state.

https://user-images.githubusercontent.com/273573/139044143-058f1738-b739-406d-a8b4-f17e253bf4f1.mp4

this message flashes on timeout or manual close
![image](https://user-images.githubusercontent.com/273573/139044865-90020909-9ae6-41ef-