Machine config

Prerequisites:
nix
brew (macOS)

Install:
Run `make HOST=<host>`

On Linux you can run GNUMake by adding it to the environment
`nix-shell -p gnumake`

Post-install:
- Configure macOS display settings

- Set up macOS keyboard shortcuts
  - Tiling
  - Mission control space switching

- Configure Finder sidebar

- Configure Firefox toolbars

- Add GitHub SSH keys