Editor: Allow name attribute on the details element in KSES.

The `details` element supports the exclusive accordion behavior among multiple `details` elements by setting a common `name` attribute. The ability to set the `name` attribute in the Details block was added in of Gutenberg 20.2. However, when a user without `unfiltered_html` attempts to save the post, the `name` attribute gets erroneously stripped out. This prevents that. 

See [WordPress/gutenberg#56969 Details block: Exclusive accordions].

Follow-up to [14406], [59775].

Props soean.
See #12835, #62887.
Fixes #64127.


git-svn-id: https://develop.svn.wordpress.org/trunk@61051 602fd350-edb4-49c9-b593-d223f7449a82

Author: westonruter

src/wp-includes/kses.php

@@ -149,6 +149,7 @@
 		'details'    => array(
 			'align' => true,
 			'open'  => true,
+			'name'  => true,
 		),
 		'div'        => array(
 			'align'   => true,