Themes: Support :focus-visible in theme.json.

Add the `:focus-visible` pseudo selector as a valid element in the `theme.json` schema. See also WordPress/gutenberg#68521.

Props huubl, audrasjb, poena, sabernhardt, afercia, annebovelett. 
Fixes #62906.

git-svn-id: https://develop.svn.wordpress.org/trunk@59854 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-includes/class-wp-theme-json.php

@@ -578,7 +578,7 @@ class WP_Theme_JSON {
 	/**
 	 * Defines which pseudo selectors are enabled for which elements.
 	 *
-	 * The order of the selectors should be: link, any-link, visited, hover, focus, active.
+	 * The order of the selectors should be: link, any-link, visited, hover, focus, focus-visible, active.
 	 * This is to ensure the user action (hover, focus and active) styles have a higher
 	 * specificity than the visited styles, which in turn have a higher specificity than
 	 * the unvisited styles.
@@ -588,11 +588,12 @@ class WP_Theme_JSON {
 	 *
 	 * @since 6.1.0
 	 * @since 6.2.0 Added support for ':link' and ':any-link'.
+	 * @since 6.8.0 Added support for ':focus-visible'.
 	 * @var array
 	 */
 	const VALID_ELEMENT_PSEUDO_SELECTORS = array(
-		'link'   => array( ':link', ':any-link', ':visited', ':hover', ':focus', ':active' ),
-		'button' => array( ':link', ':any-link', ':visited', ':hover', ':focus', ':active' ),
+		'link'   => array( ':link', ':any-link', ':visited', ':hover', ':focus', ':focus-visible', ':active' ),
+		'button' => array( ':link', ':any-link', ':visited', ':hover', ':focus', ':focus-visible', ':active' ),
 	);
 
 	/**