fixed missing pyi files in python wheel

[Ovizro]

No description provided.

[or-else]

Could you please explain the use case which requires this change?

[Ovizro]

This is related to my last pull request #863. Before I tried to add the generation of the pyi file when the python module was generated, but when I tested the packaging of the python module, I found that the pyi file was not correctly packaged into the wheel. So I appended this change.

The core changes only exist in setup.py, where I append the pyi file in package data. I modified the module generation command in README.md to be consistent with the generation script. As for the .gitignore file, I would delete it if you don't want it there.

[or-else]

Yes, please remove .gitignore or move in to py_grpc. Thanks!

[or-else]

Thanks!