I get how to use Code by Zapier as an action within a zap, but how do you use it as a trigger? I can set it up easily, but I am confused as to how & when the zap actually knows to start running on it's own? In other words, what tells the zap to start running? In other triggers typically it's a webhook sent to Zapier, but there are no webhooks involved with "Code by Zapier."
