`pydantic_model_creator` should support JSONField annotation (type hints)

Is your feature request related to a problem? Please describe.

The types of JSONField are all displayed as Any in swagger:

I need to import openapi.json into a TypeScript project for use, and this makes the generated openapi.json very poor in usability.

Describe the solution you'd like

I found in tortoise/contrib/pydantic/creator.py has

        # Json fields
        elif field_type is JSONField:
            properties[fname] = Any

I think we can avoid any by adding an optional type json_schema when defining the field, like this:

Or is there any better way to achieve this?

Start in tortoise/contrib/pydantic/creator.py at the JSONField branch that currently assigns Any. Read how field annotations are defined and how generated schemas become OpenAPI, then determine how an optional JSONField type hint should be represented. Done means JSONField annotations produce more useful types in the generated openapi.json instead of Any.