Get velocity of the ground at a geoposition.

[Dunbaratu]

Right now you can get a geopositions' XYZ pos with a :position suffix.
For completeness we should add a :velocity suffix for the XYZ velocity of the ground at that location.

It should be a kOS.Suffixed.OrbitableVelocity not just a single vector. (just like ship:velocity) so you have to specify if you meant :surface or :obt.

The useful one is probably :obt, but :surface might be useful in cases where SHIP isn't close to the geoposition right now. (Because using the :surface suffix will give us the velocity in the frame of reference of surface rotation where the ship is, not where the geoposition is, so it won't always be zero like you might expect at first glance. It would only be zero if the ship is currently sitting right at the geoposition.)

This information can be derived in a script by knowing the planet's rotational period and the radius to the center at the geoposition (sea level radius plus geoposition's altitude), and some vector operations to find out which way is the eastward unit vector at that spot, but that's a lot of extra steps to get around the fact that we don't provide it.