Build wheels for variety of platforms using cibuildwheel

I just came across this project and saw #25. I've set up building wheels on CI for a variety of projects so figured I'd send over a quick PR. This PR provides a working demo of using cibuildwheel to build wheels on CI for a matrix of Python 3.6 through 3.9, PyPy, CPython, Windows, Linux, Mac, and Mac ARM.

Example output from this Github Actions run: artifact.zip (you can only download output if it's your own repo I think)

Contains these files:

ciso8601-2.2.0-cp36-cp36m-macosx_10_9_x86_64.whl
ciso8601-2.2.0-cp36-cp36m-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl
ciso8601-2.2.0-cp36-cp36m-win_amd64.whl
ciso8601-2.2.0-cp37-cp37m-macosx_10_9_x86_64.whl
ciso8601-2.2.0-cp37-cp37m-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl
ciso8601-2.2.0-cp37-cp37m-win_amd64.whl
ciso8601-2.2.0-cp38-cp38-macosx_10_9_universal2.whl
ciso8601-2.2.0-cp38-cp38-macosx_10_9_x86_64.whl
ciso8601-2.2.0-cp38-cp38-macosx_11_0_arm64.whl
ciso8601-2.2.0-cp38-cp38-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl
ciso8601-2.2.0-cp38-cp38-win_amd64.whl
ciso8601-2.2.0-cp39-cp39-macosx_10_9_universal2.whl
ciso8601-2.2.0-cp39-cp39-macosx_10_9_x86_64.whl
ciso8601-2.2.0-cp39-cp39-macosx_11_0_arm64.whl
ciso8601-2.2.0-cp39-cp39-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl
ciso8601-2.2.0-cp39-cp39-win_amd64.whl
ciso8601-2.2.0-pp37-pypy37_pp73-macosx_10_9_x86_64.whl
ciso8601-2.2.0-pp37-pypy37_pp73-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl
ciso8601-2.2.0-pp37-pypy37_pp73-win_amd64.whl
ciso8601-2.2.0.tar.gz

Notes:

cibuildwheel was somewhat recently added to the pypa organization, so it's likely to be well maintained into the future.
cibuildwheel v2 doesn't support deprecated Python versions such as Python 2.7 or 3.5. So the wheels built are for Python 3.6+.
I see you currently use CircleCI. cibuildwheel supports CircleCI, but only on Linux and MacOS, and doesn't support Windows. I've used Github Actions more, so it was both faster to provide a demo using that and it also shows that you can build Mac, Windows, and Linux wheels with it.
To test, you can download the wheel for your platform/Python version and call pip install ./abc.whl.

Ref: https://github.com/closeio/ciso8601/issues/97

closeio / ciso8601

Build wheels for variety of platforms using cibuildwheel #109

Notes: