Feature request: async intersection check

[michaelthatsit]

We have some heavy meshes in our app. even with optimization and bvh we still see a dip in fps from time to time whenever interacting with those assets.

What I'm suggesting is an asyncPointers flag in XRStore that runs the intersection check in an async function when enabled.

This can definitely lead to some weirdness and unexpected behavior in some cases, so I'm not suggesting it be the default, but I've done it in previous THREE.js project and it worked pretty well and reliably for what we needed, and we gained back the perf we lost whenever we did Raycaster.intersectObjects()