Add new entry for PyPy 3.8?

[astrofrog]

It looks like Numpy 1.22 might now have wheels for PyPy 3.8? If so, we should update the following entry:

numpy; python_version>='3.8' and platform_python_implementation=='PyPy'

and add an explicit entry for 3.8. I don't have time to do it at the moment, but if someone else would like to take the lead on it please do so! :)

[rgommers]

Thanks @astrofrog. Indeed, the whole 1.21.x series has pypy73 wheels, and the whole 1.22.x series pypy38 wheels.

@mattip is there any preference for which numpy version to build against? Normally I'd suggest 1.22.0, but maybe there are bug fixes in later versions that are needed for PyPy 3.8?

[mattip]

1.22.0 should be OK for pypy3.8, pypy3.9

[rgommers]

Closed by gh-57