Optimize Collision Detection in JS with a Grid

To improve the performance of collision detection, we need to dive into the internals of the algorithm. Here we update the JS collision detection code to use a grid for collision detection, which brings a big performance boost at the end.

Demo repo: https://github.com/guybedford/wasm-demo

Note the demo is currently only supported in Chrome Canary with the Experimental Web Platform flag (chrome://flags/#enable-experimental-web-platform-feature) enabled due to the use of ES modules and WebGL 2.0.