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/cursorline.lua

@@ -0,0 +1,19 @@
+-- Highlight cursor words and lines
+-- https://github.com/yamatsum/nvim-cursorline
+return {
+  "yamatsum/nvim-cursorline",
+  config = function()
+    require("nvim-cursorline").setup({
+      cursorline = {
+        enable = false,
+        timeout = 1000,
+        number = false,
+      },
+      cursorword = {
+        enable = true,
+        min_length = 3,
+        hl = { underline = true },
+      },
+    })
+  end,
+}