Incorrect relative SetVelocity behaviour

[squiddingme]

It's fairly common behaviour to do some variation of Networking.LocalPlayer.SetVelocity(Networking.LocalPlayer.GetVelocity() + impulse) to add an impulse to the player's existing velocity. This can be done every frame to add a continuous force to the player, which works in VRChat but does not work in client sim. In client sim, the player will instead drift away into the sky, This completely breaks many Udon scripts that rely on manipulating standard player physics (i.e. they do not hijack player movement by putting them in a station or teleporting every frame).