Typing annotations

[ediskandarov]

I've created typing annotations for LambdaContext and corresponding classes.

https://github.com/toidi/awslambdaric-stubs

It's useful in lambda handlers:

import typing
if typing.TYPE_CHECKING:  # pragma: no cover
    from awslambdaric.lambda_context import LambdaContext

def lambda_handler(event: dict, context: "LambdaContext") -> typing.Any:
    print(context.memory_limit_in_mb)
    ...

Perhaps, it would be better to move typing definition in this repository?