Refactor simulation code into web-worker.

[kochie]

The code to calculate the kinematics of the system should be placed into a web-worker that's separate from the rendering code. Currently the kinematics are calculated in a separate interval loop

const intervalId = setInterval(calculate(), timeStep)

while the rendering of the particles is done in an animation frame loop

function animate() {
    updateMeshPositions()
    requestAnimationFrame(animate)
}

What should happen is the kinematic code should be entirely contained in a web-worker and every 1/60 of a second it should send the updated positions of the mesh to the renderer.

while (true) {
    const positions = calcKinematics()
    postMessage(positions)
}

var myWorker = new Worker('worker-kinematics.js');

myWorker.onmessage = function(e) {
    const positions = e.data
    updateMeshPositions()
}

function animate() {
    requestAnimationFrame(animate)
}