Displays an A-Z archive of narrators, with their associated books listed underneath.
Optional Attributes:
- reviewer – The login name of the reviewer to fetch posts from.
 - orderby – How to order the list of books under each author. Accepted values are: title (default), author (WordPress post author), ID (for post ID), date (post publication date), rand (random), comment_count. Or any other values listed in the WP Query docs.
 - order – Either ASC or DESC.
 - showempty – Whether or not to hide the letters that don’t have any results/authors.
 
Example:
[index-narrator orderby="rand"]