Posts: Allow the list of wrapper blocks to be filtered.

This introduces the `excerpt_allowed_wrapper_blocks` filter for controlling which blocks should be considered wrapper blocks.

Wrapper blocks and their nested contents are not stripped by `excerpt_remove_blocks()`, allowing their contents to appear in generated excerpts.

Follow up to [51348].

Props aristath, jorbin.
See #53604.
Built from https://develop.svn.wordpress.org/trunk@51375


git-svn-id: http://core.svn.wordpress.org/trunk@50986 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/blocks.php

@@ -716,6 +716,16 @@ function excerpt_remove_blocks( $content ) {
 		'core/group',
 	);
 
+	/**
+	 * Filters the list of blocks that can be used as wrapper blocks, allowing
+	 * excerpts to be generated from the `innerBlocks` of these warppers.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param array $allowed_wrapper_blocks The list of allowed wrapper blocks.
+	 */
+	$allowed_wrapper_blocks = apply_filters( 'excerpt_allowed_wrapper_blocks', $allowed_wrapper_blocks );
+
 	$allowed_blocks = array_merge( $allowed_inner_blocks, $allowed_wrapper_blocks );
 
 	/**

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51372';
+$wp_version = '5.9-alpha-51375';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.