Customizer: Make the widgets "Reorder" and "Add a Widget" buttons... buttons.

For accessibility, UI controls should preferably be native controls. Adds
ARIA attributes and labels to improve accessibility and pair these buttons
with the ones in the Menu Customizer.

Props obenland, TomHarrigan, sanket.parmar, metodiew, afercia.

Fixes #33327.

git-svn-id: https://develop.svn.wordpress.org/trunk@35304 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-customize-widgets.php

@@ -674,6 +674,10 @@ final class WP_Customize_Widgets {
 				'widgetMovedUp'    => __( 'Widget moved up' ),
 				'widgetMovedDown'  => __( 'Widget moved down' ),
 				'noAreasRendered'  => __( 'There are no widget areas currently rendered in the preview. Navigate in the preview to a template that makes use of a widget area in order to access its widgets here.' ),
+				'reorderModeOn'    => __( 'Reorder mode enabled' ),
+				'reorderModeOff'   => __( 'Reorder mode closed' ),
+				'reorderLabelOn'   => esc_attr__( 'Reorder widgets' ),
+				'reorderLabelOff'  => esc_attr__( 'Close reorder mode' ),
 			),
 			'tpl' => array(
 				'widgetReorderNav' => $widget_reorder_nav_tpl,