Add a new documentation guide

Problem/Motivation

A guide to the Drupal 10 version of the module should be created using the new documentation system.

https://www.drupal.org/drupalorg/docs/content/documentation#contrib →

A guide to the Drupal 7 version of the module exists at http://drupal.org/node/1463042, and uses the old documentation format. That guide can be sunset when Drupal 7 reaches end of life. It is not worth the effort to migrate that guide to the new format.