Add support for a power button

[anujdeshpande]

This would send a safe shutdown command to our supervisor API, and it would also have the ability to use the button to turn on the power rails that the coproc controls

[anujdeshpande]

hey @Bucknalla @phil-d-wilson
We discussed adding this feature here in yesterday's product call. There's some more stuff that we could be doing around this in some of our other products, but adding this is a good start.
I am not sure if you guys have plans for adding support for buttons, or similar. I'd love to help in any way I can.
cc @chrisys

[Bucknalla]

@anujdeshpande we basically already do a somewhat graceful shutdown of the supervisor when we flash the device - I have an idea how to extend this to firmata as we already support digital IO so it shouldn't be awfully hard to do this.

[anujdeshpande]

hey @Bucknalla - We don't use FreeRTOS/CMSIS on the firmata flash right? I saw this folder and was slightly thrown off because I didn't see anything RTOS-y in the source folder.

Reason why I ask is I was thinking of using this component from IDF - https://github.com/espressif/esp-rainmaker/tree/master/components/button
It does some nice things like like timer events so that we can have short press, long press, etc easily.

[Bucknalla]

@anujdeshpande no we don't use an RTOS

[jellyfish-bot]

[anujdeshpande] This issue has attached support thread https://jel.ly.fish/26492314-c6b3-434d-9b51-dadcfb61e4ac