Add joint keypoints config

[hdefazio]

TODO: Read this instead of hard coding the joint names

[cameron-a-johnson]

Files where this joint set is hard-coded and needs to be changed:

• [ ] https://github.com/PTG-Kitware/angel_system/blob/master/ros/angel_system_nodes/angel_system_nodes/pose_estimation/pose_estimator.py#L110
• [ ] https://github.com/PTG-Kitware/angel_system/blob/99697008986ea669f5f5e5c5cbbbf8025d9b874d/angel_system/data/common/kwcoco_utils.py#L216
• [ ] https://github.com/PTG-Kitware/angel_system/blob/99697008986ea669f5f5e5c5cbbbf8025d9b874d/ros/angel_utils/nodes/simple_2d_detection_overlay.cxx#L70
• [ ] https://github.com/PTG-Kitware/angel_system/blob/99697008986ea669f5f5e5c5cbbbf8025d9b874d/angel_system/activity_classification/utils.py#L270
• [ ] https://github.com/PTG-Kitware/angel_system/blob/99697008986ea669f5f5e5c5cbbbf8025d9b874d/ros/angel_system_nodes/angel_system_nodes/activity_classification/activity_classifier_tcn.py#L188
• [ ]