Add wp.a11y.speak() for audible alerts/updates in screen readers. Props afercia, GrahamArmfield (for the idea), iseulde. Fixes #31368.

git-svn-id: https://develop.svn.wordpress.org/trunk@31594 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/js/wp-a11y.js

@@ -0,0 +1,46 @@
+window.wp = window.wp || {};
+
+( function ( wp, $ ) {
+	'use strict';
+
+	var $container;
+
+	/**
+	 * Update the ARIA live notification area text node.
+	 *
+	 * @since 4.2.0
+	 *
+	 * @param {String} message
+	 */
+	function speak( message ) {
+		if ( $container ) {
+			$container.text( message );
+		}
+	}
+
+	/**
+	 * Initialize wp.a11y and define ARIA live notification area.
+	 *
+	 * @since 4.2.0
+	 */
+	$( document ).ready( function() {
+		$container = $( '#wp-a11y-speak' );
+
+		if ( ! $container.length ) {
+			$container = $( '<div>', {
+				id: 'wp-a11y-speak',
+				role: 'status',
+				'aria-live': 'polite',
+				'aria-relevant': 'all',
+				'aria-atomic': 'true',
+				'class': 'screen-reader-text'
+			} );
+
+			$( document.body ).append( $container );
+		}
+	} );
+
+	wp.a11y = wp.a11y || {};
+	wp.a11y.speak = speak;
+
+} )( window.wp, window.jQuery );