[feature request] Turn Frame off without the dock

[One-nb]

User wants to effectively turn Frame off without the dock. The sleep setting becomes impossible when placed somewhere in motion, e.g. pocket.

Related:
#147

Suggested from:
https://discord.com/channels/963222352534048818/984966420603482182/1251302847040192736

[siliconwitch]

Unfortunately then there'd be no way to turn Frame back on.

A way around this is the use the current frame.sleep() function, but then on startup, use the IMU as a filter to detect the orientation. If Frame is in a sideways orientation, just call frame.sleep() again