Supporting PBR

### The feature, motivation and pitch

Hi,

It would be great if Mujoco could start supporting different texture pbr maps, either through tags, or by directly supporting gltf/glb objects.

This would greatly open up a lot more types of simulations to happen inside of mujoco.

Thank you!

### Alternatives

Currrently, I'm using genesis and isaac sim as an alternative, but in terms of ease of use, and accuracy in simulations, I would love for this to exist in mujoco.

### Additional context

_No response_