[wespeaker] add __init__.py

[cdliang11]

No description provided.

[cdliang11]

Fix the error:

pip install git+https://github.com/wenet-e2e/wespeaker.git

> wespeaker --task embedding --audio_file ./1000003_0f90da0d.wav --output_file aa.txt
Traceback (most recent call last):
  File "/home/user/app/app.py", line 17, in <module>
    import wespeaker
  File "/home/user/.local/lib/python3.10/site-packages/wespeaker/__init__.py", line 1, in <module>
    from wespeaker.cli.speaker import load_model  # noqa
  File "/home/user/.local/lib/python3.10/site-packages/wespeaker/cli/speaker.py", line 30, in <module>
    from wespeaker.models.speaker_model import get_speaker_model
ModuleNotFoundError: No module named 'wespeaker.models'