Mousepick example

[mattrossman]

I'm trying to implement something like the official mouse pick example from CANNON.js. Here's the broken sandbox I've made so far:

https://codesandbox.io/s/use-cannon-mouse-picker-attempt2-jeyxy

As you'll notice the cube randomly disappears sometimes (probably because of how I hide the cursor off in the distance to avoid showing it "animating in" on each drag, which happened when I simply toggled visibility). All of the workarounds that I try just lead to new issues, so I'm done fighting with the API and would appreciate some help with how to properly recreate this.

Here's the original example I'm loosely following: https://pmndrs.github.io/cannon-es/examples/threejs_mousepick