Add 'linkTarget' property to core/button block in $allowed_blocks

lib/compat/wordpress-6.5/blocks.php

@@ -63,7 +63,7 @@ function gutenberg_process_block_bindings( $block_content, $block, $block_instan
 			'core/paragraph' => array( 'content' ),
 			'core/heading'   => array( 'content' ),
 			'core/image'     => array( 'url', 'title', 'alt' ),
-			'core/button'    => array( 'url', 'text' ),
+			'core/button'    => array( 'url', 'text', 'linkTarget' ),
 		);
 
 		// If the block doesn't have the bindings property or isn't one of the allowed block types, return.