Update docs for all accepted styles of metadata

[kkappler]

The documentation could be expanded. This would be particularly helpful if someone wanted to build a UI based on the mt_metadata schema.

Here are some things that could be updated:

• [ ] style could add reference to: name list, number list
• [ ] options only refers to controlled vocabulary (which is like typing.Literal), and seems also relevant to some cases of name list.
• [ ] ACCEPTED_STYLES and REQUIRED_KEYS in the init.py should be described in detail in the docs ACCEPTED_STYLES = [ "name", "url", "email", "number", "date", "free form", "time", "date time", "name list", "number list", "controlled vocabulary", "alpha numeric", ] REQUIRED_KEYS = [ "attribute", "type", "required", "units", "style", "description", "options", "alias", "example", "default", ]