feat(lib): add mkOpt function

lib/module/default.nix

@@ -0,0 +1,16 @@
+{
+  lib,
+  ...
+}: with lib;
+rec {
+  ## Create a NixOS module option. (Stolen from Jake Hamilton)
+  ##
+  ## ```nix
+  ## lib.mkOpt nixpkgs.lib.types.str "My default" "Description of my option."
+  ## ```
+  ##
+  #@ Type -> Any -> String
+  mkOpt =
+    type: default: description:
+    mkOption { inherit type default description; };
+}