Index: wordpress.org/public_html/wp-content/plugins/handbook/handbook.php
===================================================================
--- wordpress.org/public_html/wp-content/plugins/handbook/handbook.php	(revision 7329)
+++ wordpress.org/public_html/wp-content/plugins/handbook/handbook.php	(working copy)
@@ -241,6 +241,7 @@
 			),
 			'delete_with_user'  => false,
 			'supports'          => array( 'title', 'editor', 'author', 'thumbnail', 'page-attributes', 'custom-fields', 'revisions', 'wpcom-markdown' ),
+			'show_in_rest'      => true,   
 		);
 		// Allow customization of the default post type configuration via filter.
 		$config = apply_filters( 'handbook_post_type_defaults', $default_config, $slug );