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/legendary.lua

@@ -0,0 +1,17 @@
+-- A legend for your keymaps, commands, and autocmds
+-- https://github.com/mrjones2014/legendary.nvim
+return {
+  "mrjones2014/legendary.nvim",
+  dependencies = {
+    "kkharji/sqlite.lua",
+  },
+  keys = {
+    -- stylua: ignore
+    -- { "<leader>L", "<cmd>Legendary<cr>", desc = "Legendary" },
+  },
+  config = function()
+    require("legendary").setup({
+      which_key = { auto_register = true },
+    })
+  end,
+}