Flight path vector for FrSky S.Port telemetey

[teckel12]

Is your feature request related to a problem? Please describe

Flight path vector only works on Crossfire, make it work on FrSky S.Port

Describe the solution you'd like

Flight path vector added to S.Port

Describe alternatives you've considered

Don't offer support on S.Port telemetry

Additional context

For this to work, a YAW sensor will need to be added to INAV. Not a huge deal, as there's already a switch to replace the accelerometer values (which are never used anyway) with ROLL and PITCH. Just add YAW as well.

Flight path vector is established when comparing YAW (direction pointing) with Hdg (direction heading).

As a bonus with FrSky S.Port support, the flight path vector could use the vario data to also calculate the pitch of the flight path vector (not just the yaw). Actually, this could be done in a basic way on Crossfire too even without a vario sensor using historical altitude data. May work even better as altitude changes can be averaged out. Will look into...

[teckel12]

Vertical speed now included with latest Crossfire Rx firmware and INAV, so introducing vertical speed into the calculation of the flight path vector is now possible.