feat(nix): nix and back again

I tried Nix, but it had too many downsides so I removed it.

1. Didn't like that all files are immutable and simple config changes
need a complete rebuild.
2. Setting up a new Mac didn't work as smoothly as promised. Not worth
the effort.
3. It sucked a lot to always have to type in the password twice on each
darwin-rebuild
4. It solves problems I never had.

.config/lf/previewer.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+case "$1" in
+*) bat --force-colorization --paging=never --style=changes,numbers \
+	--terminal-width $(($2 - 3)) "$1" && false ;;
+esac