Function mh_z19::calibrate_span_point

pub fn calibrate_span_point(device_number: u8, value: u16) -> Packet

Create a command to calibrate the span point.

Quoting the datasheet: "Note: Pls do ZERO calibration before span calibration Please make sure the sensor worked under a certain level co2 for over 20 minutes.

Suggest using 2000ppm as span, at least 1000ppm"