Flight: KISS ESC Passthrough

[tracernz]

Would be super nice/useful.

[glowtape]

AFAIK KISS ESC passthrough is just hail-mary send over serial. Means when the PWM line is high when the ESC boots up, it goes into serial/flashing mode, and then writes whatever comes over the wire. There isn't any bidirectional communication a la BLHeli. At least that's how it went with my KISS24A, which I flashed with a FTDI, but it doesn't sound like this changed.