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/lsp-progress.lua

@@ -0,0 +1,7 @@
+return {
+  "linrongbin16/lsp-progress.nvim",
+  dependencies = { "nvim-tree/nvim-web-devicons" },
+  config = function()
+    require("lsp-progress").setup()
+  end,
+}