support aarch64 builds

[louisabraham]

Hello!

I'm trying to install blis (from spaCy) on a CI env and I would rather not have to require gcc.

I cannot find the aarch64 whl files on pypi and actually the latest commit here removes support for aarch64: ee825f0

[honnibal]

We've stopped hosting our own Github Actions runners, so we can't support Linux aarch64 until Github Actions has default support for it. It's currently in beta for private orgs but isn't enabled for public repos yet. Once it is we'll be able to add those wheels back.

[ajbeach2]

removing aarch64 breaks pip install on docker images on apple silicone:

#117