title: send notification if a trigger repeated for third time in zabbix
body: <p>I have several hosts on Zabbix that send to me notifications on slack.
  for some triggers severity like warning or average, I would like to receive a notification if a trigger is repeated for the third time.and for other severities like high or disaster I would like to receive a notification every time a trigger happened.
  How can this be done?</p>