Expose static contact softness in the JavaScript bindings

[stephenenglish]

Would you be open to a small PR exposing Rapier's contact softness settings through the WASM/TypeScript bindings?

Rapier 0.35 has separate contact_softness and static_contact_softness settings. The latter makes it possible to tune contacts against fixed floors and walls without also changing contacts between dynamic bodies.

The Python bindings expose both profiles, but the JavaScript bindings currently only expose the existing contact_natural_frequency setter. There is no access to the damping ratio or to the static-contact profile.

I'd propose exposing the natural frequency and damping ratio for both profiles on IntegrationParameters, while keeping the existing setter for compatibility. This would only expose the existing core settings; it wouldn't change any defaults or solver behavior.

This came up while investigating load-bearing stacks where it would be useful to tune support-to-floor contacts separately from object-to-object contacts. Since the same control is already public in core and exposed by the Python bindings, it seems useful to make it available to JavaScript users as well.

If that API shape sounds reasonable, I'm happy to put together a small PR with the WASM/TypeScript wiring and tests.

References:

• Core field: https://github.com/dimforge/rapier/blob/v0.35.0/src/dynamics/integration_parameters.rs#L202-L209
• Python binding: https://github.com/dimforge/rapier/blob/v0.35.0/python/rapier-py-3d/src/dynamics.rs#L1362-L1384
• Current TypeScript/WASM binding: https://github.com/dimforge/rapier/blob/master/typescript/src/dynamics/integration_parameters.rs