function getWGLContext(canvas) {
  if (!WGL_SUPPORTED) {
    throw new Error("Your browser doesn't support WebGL.");
  }
  const opts = {
    alpha: false,
    antialias: false,
    premultipliedAlpha: false,
    stencil: false,
    preserveDrawingBuffer: false
  };
  return (
    canvas.getContext("webgl", opts) ||
    canvas.getContext("experimental-webgl", opts)
  );
}
Creates and returns an webgl context
@param {HTMLCanvasElement} canvas
@return {WebGLRenderingContext}