Support exporting in Dataclasses instead of TypedDict

[nettrino]

Thank you for this utility - its really useful! Since TypedDict classes can contain only type annotations, it would be useful to allow exporting in dataclass format (either native or something like mashumaro's DataClassJSONMixin).

[nettrino]

I'm starting some dirty PoC in https://github.com/nettrino/gql_schema_codegen/tree/nettrino/dataclasses