reference cron alternatives

docs/configuration/procfile.md

@@ -55,6 +55,11 @@ A `cron` worker is a process that runs at a specific time (or intervals), using
 !!! warning
     `crontab` expressions are simplified and do not support ranges or lists, only single values, splits and `*` (wildcard).
 
+#### alternatives
+```Python```
+[apscheduler](https://github.com/agronholm/apscheduler) - Provides it's own library for scheduling jobs, and honors the full regex of crontab.
+
+
 ### `preflight`
 
 `preflight`  is a special "worker" that is run once _before_ the app is deployed _and_ dependencies are installed (can be useful for cleanups, like resetting caches, removing older versions of files, etc).