feat: update class comments for drush command

src/Commands/SubThemeCommands.php

@@ -18,7 +18,15 @@
 use Symfony\Component\Finder\Finder;
 
 /**
- * Defines Drush commands for generating emulsify subtheme.
+ * A Drush commandfile.
+ *
+ * In addition to this file, you need a drush.services.yml
+ * in root of your module, and a composer.json file that provides the name
+ * of the services file to use.
+ *
+ * See these files for an example of injecting Drupal services:
+ *   - http://cgit.drupalcode.org/devel/tree/src/Commands/DevelCommands.php
+ *   - http://cgit.drupalcode.org/devel/tree/drush.services.yml
  */
 class SubThemeCommands extends DrushCommands implements BuilderAwareInterface {