Add note about dir change in Drush 12 (#5696)

* Add note about dir change in Drush 12

* indent

docs/commands.md

@@ -2,7 +2,8 @@
 
 !!! tip
 
-    Drush 11 and prior required [dependency injection via a drush.services.yml file](https://www.drush.org/11.x/dependency-injection/#services-files). This approach is deprecated in Drush 12 and will be removed in Drush 13. See [create() method](dependency-injection.md#create-method).
+      1. Drush 11 and prior required [dependency injection via a drush.services.yml file](https://www.drush.org/11.x/dependency-injection/#services-files). This approach is deprecated in Drush 12 and will be removed in Drush 13. See [create() method](dependency-injection.md#create-method).
+      1. Drush 12 expects all commandfiles in the <module-name>/Drush/<Commands|Generators> directory. The `Drush` subdirectory is a new requirement.
 
 Creating a new Drush command is easy. Follow the steps below.