Add support for a fields arg in the decorators

[mhdismail]

I think supporting fields/exclude like in DRF and Graphene is a nice feature to have. I did implement the fields arg locally like the following

    dataclass_fields = list(_get_fields(django_type).values())

    if fields == '__all__':
        model_fields = list(model._meta.fields)
    elif isinstance(fields, collections.abc.Sequence) and len(fields) > 0:
        model_fields = [f for f in model._meta.fields if f.name in fields]
    else:
        model_fields = list()

    cls.__annotations__ = {}

    # update annotations and fields
    for f in dataclass_fields:
        annotation = f.type_annotation.annotation if f.type_annotation else f.type
        if annotation is None:
            annotation = StrawberryAnnotation(strawberry.auto)

        cls.__annotations__[f.name] = annotation
        setattr(cls, f.name, f)
    
    for f in model_fields:
        if cls.__annotations__.get(f.name):
            continue

        annotation = resolve_model_field_type(f, django_type)
        if not annotation:
            continue

        cls.__annotations__[f.name] = annotation
        setattr(cls, f.name, f.default or None)

now you can can do

@model_type(
    models.Foo, filters=FooFilter, order=FooOrder, pagination=True,
    fields='__all__'
)
class FooType(relay.Node):
    pass

@model_type(
    models.Foo,
    fields=['x', 'y', 'z']
)
class FooType(relay.Node):
    pass

I think it's a useful feature to have, what do you think? I did not test it outside queries, but I think it shouldn't be a problem.