Restructure Darwin configuration

So far, this is just based on mightymac. The other devices will be
updated soon.

modules/hosts/common/files/nvim/lua/disabled/nvim-tree.lua

@@ -0,0 +1,11 @@
+return{
+  "nvim-tree/nvim-tree.lua",
+  config = function ()
+    vim.g.loaded_netrw = 1
+    vim.g.loaded_netrwPlugin = 1
+
+    require('nvim-tree').setup()
+
+    vim.keymap.set('n', '<c-n>', ':NvimTreeFindFileToggle<CR>')
+  end
+}