Literal (and Union[Literal]) support

[davetapley]

Feature request for:

@dataclass
class HasLiteral:
  foo: Literal["one"]

jsons.loads('{"foo": "one"}', HasLiteral)

Currently gives:

DeserializationError: No deserializer for type "typing.Literal"

And more realistic use case:

@dataclass
class HasLiteral:
  foo: Union[Literal["one"], Literal["two"]]

Currently gives:

DeserializationError: Could not match the object of type "str" to any type of the Union: Literal, Literal

---

I can have a go if a PR would be accepted?

[ramonhagenaars]

Hi @davetapley. I think your feature request makes sense, I would gladly accept a PR on this 😃