Support PEP563 lazy type evaluation

[yukinarit]

Adding from __future__ import annotations to examples/simple.py raises an exception.

from __future__ import annotations
from dataclasses import dataclass

from serde import deserialize, serialize
from serde.json import from_json, to_json


@deserialize
@serialize
@dataclass
class Foo:
    i: int
    s: str
    f: float
    b: bool


def main():
    f = Foo(i=10, s='foo', f=100.0, b=True)
    print(f"Into Json: {to_json(f)}")

    s = '{"i": 10, "s": "foo", "f": 100.0, "b": true}'
    print(f"From Json: {from_json(Foo, s)}")


if __name__ == '__main__':
    main()

Into Json: {"i": null, "s": null, "f": null, "b": null}
Traceback (most recent call last):
  File "/Users/yukinari/repos/pyserde/examples/simple.py", line 27, in <module>
    main()
  File "/Users/yukinari/repos/pyserde/examples/simple.py", line 23, in main
    print(f"From Json: {from_json(Foo, s)}")
  File "/Users/yukinari/repos/pyserde/serde/json.py", line 29, in from_json
    return from_dict(c, de.deserialize(s, **opts), reuse_instances=False)
  File "/Users/yukinari/repos/pyserde/serde/de.py", line 274, in from_dict
    return from_obj(cls, o, named=True, reuse_instances=reuse_instances)
  File "/Users/yukinari/repos/pyserde/serde/de.py", line 211, in from_obj
    return serde_scope.funcs[FROM_DICT](o, reuse_instances=reuse_instances)
  File "<string>", line 16, in from_dict
  File "/Users/yukinari/repos/pyserde/serde/core.py", line 82, in raise_unsupported_type
    raise SerdeError(f"Unsupported type: {typename(type(obj))}")
serde.core.SerdeError: Unsupported type: int

[yukinarit]

PEP563 was reverted for Python 3.10 😄
https://mail.python.org/archives/list/python-dev@python.org/thread/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/