Add new contacts manually during contact modification

As mentioned in the warning found in [the docs](https://rapier.rs/docs/user_guides/bevy_plugin/advanced_collision_detection/#contact-modification), bevy-rapier does not support generating new contacts. I have a use case for such functionality. I'd like to generate contacts between rapier colliders and static implicitly defined surfaces before the solver runs.

I'll probably end up hacking in a hook to do what I want eventually, but it would be nice to avoid that. I have yet to do any investigation on how to do this in rapier and would appreciate any indication for a work-around.

To be clear, these contacts would always be between a dynamic rigidbody and a static unmoving implicitly defined surface.