Support aarch64-darwin

[chris-martin]

aarch64-darwin is not among the supported systems in flake.nix; I wonder, could it be? Some of my coworkers run this architecture locally, and GitHub Actions has runners for it now.

[hasufell]

I don't maintain the nix part. Someone else has to contribute to it.

[chris-martin]

Cool, I'll try to take a look at it.