Include crontab generator example

doc/workflow/repository_mirroring.md

@@ -92,7 +92,7 @@ While mirrors update once an hour, you can force an update (either **push** or
 
 ## Adjusting synchronization times
 
-You can manually configure the repository synchronization times by setting the following configuration values. *These are cron formatted values.* 
+You can manually configure the repository synchronization times by setting the following configuration values. *These are cron formatted values.* You can use a crontab generator to create these values, for example http://www.crontabgenerator.com/
 
 Please note that `update_all_mirrors_worker_cron` refers to the worker used for pulling changes from a remote mirror while `update_all_remote_mirrors_worker_cron` refers to the worker used for pushing changes to the remote mirror.
 
@@ -110,7 +110,7 @@ cron_jobs:
     update_all_mirrors_worker_cron:
       cron: "0 * * * *"
     update_all_remote_mirrors_worker_cron:
-      cron: "30 * * * *"   
+      cron: "30 * * * *"
 ```
 
 [ee-51]: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/51