Airport and dip switch on tx

[RobertoD91]

When using the BetaFPV 2.4 Micro TX module with Airport, it's necessary to set the DIP switches in programming mode instead of "normal" mode (in this case, DIP switches 1 and 2 should be on, and the others off).

ExpressLRS/ExpressLRS#2546

I imagine that this issue is hardware-specific, but it might be helpful for beginners like me if there were a reference in the documentation. Something as simple as "If your TX module has DIP switches, make sure to set them appropriately."