Customizer: Trigger `widget-added` event when initializing.

Widget controls are now added to the pane dynamically via JavaScript, see #28709.
Remove the event trigger from `SidebarControl.addWidget()` as it's covered by `WidgetControl.ready()`.

props westonruter.
fixes #30236.

git-svn-id: https://develop.svn.wordpress.org/trunk@30308 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -434,6 +434,12 @@
 			this._setupHighlightEffects();
 			this._setupUpdateUI();
 			this._setupRemoveUI();
+
+			/*
+			 * Trigger widget-added event so that plugins can attach any event
+			 * listeners and dynamic UI elements.
+			 */
+			$( document ).trigger( 'widget-added', [ this.container.find( '.widget:first' ) ] );
 		},
 
 		/**
@@ -1806,8 +1812,6 @@
 				}
 			} );
 
-			$( document ).trigger( 'widget-added', [ $widget ] );
-
 			return widgetFormControl;
 		}
 	} );