General imporovements

Fix file uploading!
Maybe add some logic to make it wait for the socket to be opened?
- also better error messages, that would be nice.
- and it might be cool to give you the option to open the mpv instance by yourself
Maybe write some integration tests with Nix's testing framework
Make QR code move every once in a while to avoid burn-in
Save playlist on exit and load it on start with the previous position. Maybe there's an option for this, otherwise: https://github.com/CogentRedTester/mpv-scripts/blob/master/save-playlist.lua
Package a batch file that downloads the latest mpv release and creates a start.bat file on Windows

Scope creep