Added an info comment in the empty code styles sheet.

Author: oleq

theme/code.css

@@ -2,3 +2,9 @@
  * Copyright (c) 2003-2017, CKSource - Frederico Knabben. All rights reserved.
  * For licensing, see LICENSE.md.
  */
+
+/*
+ * Note: This file should contain the wireframe styles only. But since there are no such styles,
+ * it acts as a message to the builder telling that it should look for the corresponding styles
+ * **in the theme** when compiling the editor.
+ */