Improve Parse Server Guide for Email Options, Account Lockout, PasswordPolicy 📕

References:
There are a number of options for Parse Server that are only explained on github but aren't explained at all in the Parse Server Guide.

Proposed solution:
It's my view that the Parse Server Guide should be able to explain all the server options and configuration without readers having to know to go to github. For example, if you search for "Mail options (or similar)" on the docs, nothing shows. It could be assumed that these features don't exist.

On that note, I would propose stripping back the README.md on the repo, transitioning most of the contents to the docs site, and mostly pointing the readme to the docs, such as other packages do, eg react, vue. I think only basic configuration should be shown on the github, and the rest should point to the docs site.

Compare the Parse Server options described in README.md with the Parse Server Guide, especially the email, account-lockout, and PasswordPolicy sections. Inventory the missing explanations, update the Guide accordingly, and determine which README.md content should remain or point to the documentation site.