ARM64 macOS 11 ("Apple Silicon")

It is now possible to successfully build binaries for ARM64 macOS using GitHub Actions, and this is exactly what this release does. These binaries are entirely untested since, well, nobody has an ARM64 Mac and I don't think Node.js runs on it yet. In any case - this is good preparation for the future.

• It should mean no difference to Intel macOS users unless something has regressed - please report any issue with this release regarding macOS.
• If you happen to have an ARM64 Mac; please test this if you can!