Improvements for DJAS016 (settings)

[Viicos]

Following #37:

• What to do if the project settings sets a different type from the global one? e.g. a global type is defined as str | None (default is None), but the project sets a string. Should we use the project type? Should the behavior be configurable? This also does not apply to all cases, e.g. booleans: probably doesn't make sense to set it as Literal[True/False]?
• Figure out what types can be used for PathLikes: check source code and stubs, push fixes in stubs if necessary. (This is related to the previous point).
• What about custom settings: works fine with primitives, what if lists/dicts are being used? Would be nice to parse the AST of the module where it is defined, so that docstrings can also be pulled out.

Wrong types:

• LANGUAGE_COOKIE_AGE/SESSION_COOKIE_AGE: int or timedelta