Set loading state for UI when layout select radio option is changed.

js/layout-paragraphs-widget.js

@@ -911,6 +911,12 @@
           )
           .prependTo($(layoutParagraphsItem));
       });
+    /**
+     * Set state to loading when a radio is clicked.
+     */
+    $(".layout-select input[type=radio]", $widget).change(e => {
+      setLoading($(e.target).closest(".layout-select"));
+    });
     /**
      * Only show disabled items if there are items in the field.
      * Runs every time DOM is updated.