[DOCS] Improve docs for pc.RigidBodyComponent (#936)
[DOCS] Improve docs for pc.RigidBodyComponent (#936)

Fix restitution property description and add defaults for other
properties.

aidinabedi/playcanvas-engine,sereepap2029/playcanvas,H1Gdev/engine,sereepap2029/playcanvas,guycalledfrank/engine,playcanvas/engine,MicroWorldwide/PlayCanvas,sereepap2029/playcanvas,H1Gdev/engine,MicroWorldwide/PlayCanvas,aidinabedi/playcanvas-engine,playcanvas/engine,guycalledfrank/engine