[FEATURE] Notification for workflow does not process event for a duration

**Is your feature request related to a problem? Please describe.**
If we have a workflow that should be expected to be running multiple times a day, it would be good to get a warning if for some reason it hasn't been invoked for 24 hrs, as that might indicate a problem (e.g. with a source or something else).

**Describe the solution you'd like**
Just wondering if there was any functionality in Pipedream which can monitor workflows and alert with a Slack message if there haven't been any invocations within a set period of time? E.g.

**Do you have a workaround?**
Custom workflow

**Additional context**
Requested by customer here