Fix incorrect path to Wholebody models + update README

[barakyo]

Background

When trying this out I encountered the following error:

Traceback (most recent call last):
  File "/home/user/StableAnimator/DWPose/skeleton_extraction.py", line 6, in <module>
    from dwpose_utils.dwpose_detector import dwpose_detector_aligned
  File "/home/user/StableAnimator/DWPose/dwpose_utils/dwpose_detector.py", line 57, in <module>
    dwpose_detector_aligned = DWposeDetectorAligned(device=device)
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/StableAnimator/DWPose/dwpose_utils/dwpose_detector.py", line 13, in __init__
    self.pose_estimation = Wholebody()
                           ^^^^^^^^^^^
  File "/home/user/StableAnimator/DWPose/dwpose_utils/wholebody.py", line 17, in __init__
    self.session_det = ort.InferenceSession(path_or_bytes=onnx_det, providers=providers)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/mambaforge/envs/stableanimator/lib/python3.11/site-packages/onnxruntime/capi/onnxruntime_inference_collection.py", line 465, in __init__
    self._create_inference_session(providers, provider_options, disabled_optimizers)
  File "/home/user/mambaforge/envs/stableanimator/lib/python3.11/site-packages/onnxruntime/capi/onnxruntime_inference_collection.py", line 526, in _create_inference_session
    sess = C.InferenceSession(session_options, self._model_path, True, self._read_config_from_model)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxruntime.capi.onnxruntime_pybind11_state.NoSuchFile: [ONNXRuntimeError] : 3 : NO_SUCHFILE : Load model from path/checkpoints/DWPose/yolox_l.onnx failed:Load model path/checkpoints/DWPose/yolox_l.onnx failed. File doesn't exist

It was because the path for the Wholebody models had a path/ prefix. I removed this path and ran it from the root project dir and the command worked. Because of that, I also updated the README to show that you should run it from the root project dir.

[Francis-Rings]

Hi, thank you for your contribution!