[REQUEST] Support timer API
For various reasons it would be extremely useful to trigger a countdown timer when a TP-Link smart outlet or switch to automatically turn on or off the device.

The Kasa App exposes this functionality and there is a blog post [here](https://itnerd.space/2017/06/05/remotely-control-your-hs100-timer-api/) detailing how to create timers programmatically.

Perhaps an option in the config with something like `{"timer": 300}` where `300` is the time in seconds after the state of the accessory is reset to whatever it was previously. So if the device was On, and a user changes the state to Off after 5 minutes the accessory would turn back on.