sendComment cannot send more than 62 bytes, as limited by the HID report.
Sending more is prevented by vsnprintf, but change the function signature
to make it explicit that the array passed to it should be at most 62 bytes.
Implement a set of functions to create messages following the protocols
defined in the README for communication.
Handle HID, which is used to communicate with the interactive application.
Update README with details on the message structures.