Add support for WebGPU: XRGPUBinding missing

[alienself]

Hi there!

WebGPU now has XR support, could we get an update to this library to support it?
We need to emulate XRGPUBinding which is only available on Windows / Android but not on mac.

https://toji.dev/2025/03/03/experimenting-with-webgpu-in-webxr.html

See more here:
https://github.com/immersive-web/webxr-samples/blob/main/webgpu/vr-barebones.html

A simple threejs example to test it:
https://threejs.org/examples/?q=xr#webgpu_xr_cubes

[botaohu]

+1
Important feature!