Support for GUI apps

Hi!

I just found this a few days ago, and it's pretty cool, I like that it's nix-based but can be installed and ran without any root privileges. Also that it materializes the result faster than nix itself :D

I was wondering if you're interested in supporting GUI apps, by passing through and/or adding the necessary env vars and fs binds? I managed to make this work on a NixOS host using Codex, but it didn't work on an Ubuntu host, I guess it's easier to forward the same environment that the nix packages already expect.

If you are open to supporting this, I might work a bit more to try to make it work, let me know what you think!