[Docs] PoseTracker not covered in documentation

[timsainb]

📚 The doc issue

PoseTracker is not currently in the documentation for either mmpose or mmdeploy.

The only reference that I can find for it is at https://github.com/open-mmlab/mmdeploy/blob/main/demo/python/pose_tracker.py

In particular, I can't find any information about how to set a threshold for when a detected person is transferred from the mmdetection to mmpose model.

Suggest a potential alternative/fix

No response

[Gnoot01]

Please link the pose_tracker.py referred in https://github.com/open-mmlab/mmpose/tree/main/projects/rtmpose#windows, so others can find it easier