Added closeButton option

jquery.colorbox/jquery.colorbox.d.ts

@@ -106,6 +106,10 @@ interface ColorboxSettings {
     */
     close?: string;
     /**
+    * Set to false to remove the close button.
+    */
+    closeButton?: boolean;
+    /**
     * Error message given when ajax content for a given URL cannot be loaded.
     */
     xhrError?: string;