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/cheatsheet.lua

@@ -0,0 +1,9 @@
+return {
+  "sudormrfbin/cheatsheet.nvim",
+  dependencies = {
+    'nvim-telescope/telescope.nvim',
+    'nvim-lua/popup.nvim',
+    'nvim-lua/plenary.nvim',
+  },
+  config = true,
+}