Feature request: s3 sleep option to check file based flag

[atxalex]

Would it be possible to add support so the s3_sleep script will check a file on the system for activity state before proceeding to sleep or shutdown? It would make the plugin a lot more flexible in terms of integrating with other services.
It can be a configurable filename and the file can contain a true/false flag or whatever the plugin needs.

I'm planning on pulling the plex activity stream count via api and in order to update the activity state, but there can be plenty of other ways to integrate with this.