An experimental GUI based on https://github.com/clue/reactphp-zenity has been merged with #13 quite some time ago. Unfortunately it never quite reached a state in which this should be part of this project. Also, it introduces a dependency on ext-posix which I'd like to avoid.

For now, we're going to drop the dependency again (effectively reverting #13).

This ticket serves as a reminder to re-enable the GUI feature once it's in a usable state.