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/fish/functions/encodeBase64.fish

@@ -0,0 +1,3 @@
+function encodeBase64 --description "Encodes images in Base64"
+    uuencode -m $argv[1] /dev/stdout | sed 1d | sed '$d'
+end