Add CI code style and run unit test on GA

[zhongjiajie]

We should add CI on GA about check our code style and run unit test.

I thinks maybe we should use tox as CI wrapper to run all think

, and about code style:

• use black to check and auto fix
• use flake8 to check code and docstring
• use isort about import auto sort

, about unit test

• use pytest to run tests
• show test coverage about this repo
• show current GA workflow status in readme

[zhongjiajie]

already fix