Twenty Thirteen, Twenty Sixteen: Use default display for summary element.

Within the details block, style the `summary` element using the default display, `list-item`, this ensures the toggle icon appears indicating the summary can be expanded or contracted.

Props ankit-k-gupta, nicolefurlan, poena, sabernhardt.
Fixes #58915.

Built from https://develop.svn.wordpress.org/trunk@56940


git-svn-id: http://core.svn.wordpress.org/trunk@56451 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-content/themes/twentysixteen/css/blocks.css

@@ -319,6 +319,12 @@ hr.wp-block-separator {
 	margin-bottom: 0;
 }
 
+/* Details */
+
+.wp-block-details > summary:first-of-type {
+	display: list-item;
+}
+
 /*--------------------------------------------------------------
 5.0 Blocks - Widget Blocks
 --------------------------------------------------------------*/

wp-content/themes/twentythirteen/css/blocks.css

@@ -544,6 +544,12 @@ body:not(.sidebar) .wp-block-table.alignfull {
 	margin-bottom: 0;
 }
 
+/* Details */
+
+.wp-block-details > summary:first-of-type {
+	display: list-item;
+}
+
 /*--------------------------------------------------------------
 6.0 Blocks - Widgets
 --------------------------------------------------------------*/

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-beta4-56939';
+$wp_version = '6.4-beta4-56940';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.