feat(nix): migrate Neovim to Nix (as a symlink)

nix/home/neovim/nvim/lua/plugins/copilot.lua

@@ -0,0 +1,10 @@
+-- Copilot replacement
+-- https://github.com/zbirenbaum/copilot.lua
+-- https://github.com/zbirenbaum/copilot-cmp
+return {
+  "zbirenbaum/copilot-cmp",
+  dependencies = "zbirenbaum/copilot.lua",
+  opts = function()
+    require("copilot").setup()
+  end,
+}