Add better support for `polygon` and `tuple` composite axes

[PaulVanSchayck]

See discussion here. Need to add support for polygon and tuple composite axes here

Could be either

from geojson_pydantic.types import PolygonCoords

class Axes(CovJsonBaseModel):
    ...
    composite: Optional[Union[ValuesAxis[PolygonCoords], ValuesAxis[Tuple]]]

Or

from geojson_pydantic.types import PolygonCoords

class ValuesAxisCompositePolygon(ValuesAxis):
    dataType: Literal["polygon"] = "polygon"
    values: List[PolygonCoords]

class ValuesAxisCompositeTuple(ValuesAxis):
    dataType: Literal["tuple"] = "tuple"
    values: List[Tuple]

ValuesAxisCompositeTypes = Annotated[Union[ValuesAxisCompositePolygon, ValuesAxisCompositeTuple], Field(discriminator="dataType")]

class Axes(CovJsonBaseModel):
    ...
    composite: Optional[ValuesAxisCompositeTypes]   

Both solutions have prons and cons, and also need to be checked performance wise. Would be good to also add the validation for coordinates here.