Build wheels for Linux aarch64

[bbayles]

This PR updates the Github Actions workflow to build wheels for Linux on aarch64. The motivation for me is to be able to easily deploy packages that depend on ciso8601 to AWS Lambda functions using Graviton processors.

I hope you can use this PR! I've used your package for years; it's my go-to for applications that bottleneck on parsing datetime strings.

[BoboTiG]

Would love to see this happen too :)

[wlach]

@movermeyer Any chance this could be looked at? It seems straightforward and would really be helpful in a lot of use cases. Even where it's technically possible to rebuild the wheel, it's very expensive to do it at build-time.

[bbayles]

For what it's worth, I (original PR author) have switched away from this library - the advice in the docs is correct; the Python 3.11+ datetime.fromisoformat is a suitable replacement, and for older versions there is a backport.