Add prebuilt binaries for Apple silicon

[davidanthoff]

I think with the rapid adoption of Apple silicon in Macs this would be really great. Node 16 has added support for Apple Silicon as well, so I think that end of the story should be ready.

[chearon]

Prebuilds are working for macOS/Arm since #2354 was merged!

npm install canvas@next to get 3.0.0-rc3. I'm going to wait a few days before releasing 3.0.