Re-export top-level imports to satisfy Mypy

[reivilibre]

Using Mypy (at least in strict mode) with the library as it currently is causes errors.

import aiounittest


class ExampleTest(aiounittest.AsyncTestCase):
    def test_example(self) -> None:
        self.assertEqual(1, 2 - 1)

tests/test_example.py:4: error: Name "aiounittest.AsyncTestCase" is not defined
tests/test_example.py:4: error: Class cannot subclass "AsyncTestCase" (has type "Any")

It seems to be good practice to 're-export' (using __all__) all the things that you import into a module and wish to allow others to use as an import. I don't think this is actually functionally different, but just a convention.
IDEs (auto-import feature) and Mypy pick up on this, at the very least.

Signed-off-by: Olivier Wilkinson (reivilibre) oliverw@matrix.org
I am happy for these changes to be available under the project's licence (MIT).

[kwarunek]

Great. Thx