Feature request: add glTF Sample Viewer

[echadwick-artist]

Could we add the glTF Sample Viewer to the list of renderers in the preview?
http://gltf.ux3d.io/

It would be nice to have a setting for choosing the IBL too, if possible.

Thank you!

[echadwick-artist]

There are two implementations I am aware of:

1. https://github.khronos.org/glTF-Sample-Viewer-Release/ = official Khronos release.
2. http://gltf.ux3d.io/ = early features development, for example KHR_materials_iridescence.

I think if we had to choose only one of the two, I would suggest the latter since it is likely to have the latest developments.

[echadwick-artist]

I'm re-thinking this. It would be better to implement the official release, since it's the canonical renderer.