REST API: Introduce "hex-color" JSON Schema format.

Props spacedmonkey, chrisvanpatten.
Fixes #49270.


git-svn-id: https://develop.svn.wordpress.org/trunk@47450 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/rest-api/rest-test-controller.php

@@ -64,6 +64,11 @@ class WP_REST_Test_Controller extends WP_REST_Controller {
 					'format'  => 'email',
 					'context' => array( 'view' ),
 				),
+				'somehex'        => array(
+					'type'    => 'string',
+					'format'  => 'hex-color',
+					'context' => array( 'view' ),
+				),
 				'someenum'       => array(
 					'type'    => 'string',
 					'enum'    => array( 'a', 'b', 'c' ),