Add Annotated support

[mvanderlee]

Fixes #256

Moving away from NewType and instead add Annotated support.

• https://docs.python.org/3/library/typing.html#typing.Annotated
• https://peps.python.org/pep-0593/

[mivade]

I would recommend importing Annotated from typing_extensions for Python 3.8 support (at least for as long as that continues receiving security updates).

[mvanderlee]

Rebased, and retested.

[mvanderlee]

@lovasoa @dairiki Any idea when you'll have time to review this? I'd like to see this merged so I can rebase and finalize the generic dataclass PR #259

[dairiki]

I apologize for the delay. (Life has been crazy.)

The feature addition is a good one, I think. (Thank you!) And other than some style nits, I think it looks fine.

I think the addition of tox test configuration is long overdue. Ideally, it would be a separate PR, but since it's in here, already, I'm fine leaving it here. I do have a few comments about that.

[mvanderlee]

I apologize for the delay. (Life has been crazy.)

The feature addition is a good one, I think. (Thank you!) And other than some style nits, I think it looks fine.

I think the addition of tox test configuration is long overdue. Ideally, it would be a separate PR, but since it's in here, already, I'm fine leaving it here. I do have a few comments about that.

I haven't had time since either, so I get it. Thank you for taking the time to review it!

[mvanderlee]

I think I've resolved all issues. The PR is ready for review again.

[dairiki]

In my local dev environment, I'm having a few issues with the tox.ini.

Otherwise, LGTM.

[mvanderlee]

I've removed tox.ini from this PR.

[dairiki]

Merged. Thank you, @mvanderlee !

I tried to make a new PyPI release (8.7.0) but #270 happened.

[dairiki]

Now released in 8.7.0.