inconsistency between docs and actual code for sqlite backend

[paulhersch]

Describe the bug
The sqlite connection with the config dict has the use of field "path" documented: https://tortoise.github.io/databases.html#required-parameters, but one has to use "file_path" as parameter.

To Reproduce

    "connections": {
        # dev connection
        "sqlite": {
            "engine": "tortoise.backends.sqlite",
            # path is documented, but file_path is used
            "credentials": {"path": "./dev.db.sqlite3"},
        },
    },
    "apps": {
        "myapp": {
            "models": ["myapp.db.models"],
            "default_connection": "sqlite",
        }
    },

Expected behavior
I would expect to be able to use "path" as per the documentation. It is also kind of confusing, that the path is part of the credentials, but it makes sense if you read the documentation for the other databases and the docstring of Tortoise.init. Using file_path should be part of the documentation, as i would guess user code now relies on that parameter being used.