feat: rewrite the whole code

- Now stores the different lists in a tree which caches each path to
  enable the minimum amount of re-fetching
- Every request is async allowing input while waiting for the server to
  respond
- No longer requires a list library as a list implementation is built in

Currently I've yet to implement the video handling, but that's next!

test/test.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+MPV_HOME=mpv mpv --force-window=immediate --idle --script=..