KSES: Add `writing-mode` to the list of safe CSS properties.

Original PR from Gutenberg repository:
* [https://github.com/WordPress/gutenberg/pull/54581 #54581 Gutenberg Plugin: Add hook to allow `writing-mode` as a safe CSS property]

Reference: [https://developer.mozilla.org/en-US/docs/Web/CSS/writing-mode MDN Web Docs: writing-mode].

Follow-up to [56605].

Props wildworks, mukesh27, poena, andrewserong.
Fixes #59387.
Built from https://develop.svn.wordpress.org/trunk@56617


git-svn-id: http://core.svn.wordpress.org/trunk@56129 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/kses.php

@@ -2301,6 +2301,7 @@ function kses_init() {
  *              and `z-index` CSS properties.
  * @since 6.3.0 Extended support for `filter` to accept a URL and added support for repeat().
  *              Added support for `box-shadow`.
+ * @since 6.4.0 Added support for `writing-mode`.
  *
  * @param string $css        A string of CSS rules.
  * @param string $deprecated Not used.
@@ -2461,6 +2462,7 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 			'object-position',
 			'overflow',
 			'vertical-align',
+			'writing-mode',
 
 			'position',
 			'top',

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56616';
+$wp_version = '6.4-alpha-56617';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.