Feature: Automatic clear-refresh when stream is offline for set period of time

[SleepyLili]

I think the next useful feature would be an automatic reset of the redeems queue and counters. Owncast sends events for both stream start and stream end, and the bot has a capability of checking whether stream is online, so I could add something that just clears the queue for you if you don't stream for X minutes or hours.

(maybe 15 by default? 30 to be safe and really exclude disconnects?)