Customizer: When widget reorder button is actioned, transfer focus to the first Move control within the section.

fixes #28891.

git-svn-id: https://develop.svn.wordpress.org/trunk@29242 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/js/customize-widgets.js

@@ -1586,6 +1586,8 @@
 				_( this.getWidgetFormControls() ).each( function( formControl ) {
 					formControl.collapseForm();
 				} );
+
+				this.$sectionContent.find( '.first-widget .move-widget' ).focus();
 			}
 		},