Persistent Timer

[harmonz]

Add function of "Persistent timer" as a toggle along with "Shake to reset" in the sleep timer window.
Purpose: The play button will always activate or maintain the sleep timer whether by the interface, notification, widget, or headphones.
Why this might matter: Listening at night failing to reset sleep timer makes the audiobook a part of the dream state. If the phone is out of reach to shake, the headphone play button will continue playback with sleep timer again. I may be the only person in the world who falls asleep listening to audiobooks (doubtful), but will always want a timed playback even while I'm hiking or shopping. Restarting playback is easy while awake. Stopping playback is difficult while asleep. I've never needed playback to go to the end of a 10 hour book nonstop.