Native Point Cloud Visualization in Viewer

### The feature, motivation and pitch

Could you consider adding native point cloud import and visualization (e.g., .ply or .pcd) to the MuJoCo viewer? point clouds are my primary data format to work with, and having them as a visual overlay would be great for verification. Would the team be open to implementing a vertex rendering feature to support this kind of ground-truth debugging? Currently, each vertex is render as sphere and it is not resource efficient

### Alternatives

_No response_

### Additional context

_No response_