Add WordPress custom post type to rest api
/**
* Register a book post type, with REST API support
*
* Based on example at: https://codex.wordpress.org/Function_Reference/register_post_type
*/
add_action( 'init', 'my_book_cpt' );
function my_book_cpt() {
$args = array(
'public' => true,
'show_in_rest' => true,
'label' => 'Books'
);
register_post_type( 'book', $args );
}