Set up linters for the project

[justinchuby]

It helps if we set up linters early in the development process (less big PRs for fixes in the future). We may consider: mypy, pylint, black, isort, pydocstyle, flake8, bandit and xdoctest.

[titaiwangms]

Is it like creating something this https://github.com/pytorch/pytorch/blob/master/.lintrunner.toml and it's all done?
More detail: https://github.com/suo/lintrunner

While I am still getting familiar with the whole code base, I figure I should be able to do this.

• Add flake8+isort+black+mypy (same as ONNX)
• .github/workflow/lint.yaml
• formatting all files