Improve CLI docs

Part of https://github.com/blitz-js/blitz/issues/3828

Go over each page and see how it can be improved:
- Is there a guide?
- Is the API covered?
- Make sure that the information is correct and up to date with the Blitz 2.0

Start by reviewing each CLI documentation page on the Blitz website and compare its content with Blitz 2.0. For each page, check whether a guide and API coverage exist and verify that the information is current and correct; done means the CLI documentation has been audited and the needed improvements are identified or made.

Written by the indexing model from the issue text.