blenvy: Documents for Rapier

[xx1adfasd]

Quick start and Physic Integration Documents for Rapier3d.

The steps will be almost the same.

Or, maybe using a single document and code to show both integrations.

[xx1adfasd]

Ok I find out that it seems that rapier does not have a counterpart code for "ColliderConstructor" from avian. So it will be more difficult for new users to learn blenvy. So avian is good enough for the get start document.