Docs proof reading

[xjjiang]

Summary

This PR corrects some of the insufficient information, broken links, etc. For links, I know jupyter-book can detect whether a file is an MD file or an ipynb file if file extension is not provided. But In VS Code and GitHub website, it is an borken link if a file extension is not given.

Related Issues

• Resolves #

Backwards incompatibilities

None

New Dependencies

None