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/nvim/lua/plugins/auto-save.lua

@@ -0,0 +1,8 @@
+-- 🧶 Automatically save your changes in NeoVim
+-- https://github.com/pocco81/auto-save.nvim
+return {
+  "Pocco81/auto-save.nvim",
+  keys = {
+    { "<leader>as", "<Cmd>ASToggle<CR>", desc = "Autosave Toggle" },
+  },
+}