API function on Python Viewer to inject textures independently from mjModel

[vikashplus]

The feature, motivation and pitch

The ability to add a new geom to the user_scn in the Python viewer is quite powerful in building and updating all sort of visualization needs -- from annotation to sensor data viz. We have been using this functionality extensively.

For a newly added geom, we also want to add and use a new user texture & material. This feature is currently not supported. This is a missed opportunity as it can unlock a wide variety of cool visualization features on top on simulation which should be lean and thin.

After discussion with @yuvaltassa and @saran-t, it was proposed that we use "a new API function to inject textures and materials independently from mjModel".

Starting this request to track the developments.

Alternatives

No response

Additional context

No response

[jjyyxx]

Also, allow uploading mesh independently from mjModel would be helpful to my use case.