[docs] add docs for the PRs: 1629, 1632

Improve the related docs page based on the newly merged PRs: https://github.com/casbin/casbin/pull/1629 and https://github.com/casbin/casbin/pull/1632
You should write high-quality human-like docs for a modern OSS software. Don't write in the GPT-flavor. Don't write too long, keep it tidy docs. Don't use itemized list to describe things like "Use Cases", "Best practice" or "what it can do"
don't change yarn.lock
Don't add too long text, keep it short and to the point
Don't add the docs in a template like one section name and one text paragraph. You need to organize the content to be user-friendly and not boring for users to read