Update interface for latest register spec

[bruno-f-cruz]

In particular:
vpp
frequency

[bruno-f-cruz]

@Poofjunior the firmware doesn't seem to reflect the state of these new functions yet:

harp.device.lickety-split/firmware/src/main.cpp

Lines 56 to 58 in 62e7257

	uint8_t lick_state; // app register 0
	uint8_t on_threshold; // app register 1
	uint8_t off_threshold; // app register 2

Can you confirm?

[Poofjunior]

🤦🏼 whoop--this is still in a branch. Will get this merged into main asap.