static normalize(out, a) {
    const x = a[0];
    const y = a[1];
    const z = a[2];
    const w = a[3];
    let len = x * x + y * y + z * z + w * w;
    if (len > 0) {
      len = 1 / Math.sqrt(len);
    }
    out[0] = x * len;
    out[1] = y * len;
    out[2] = z * len;
    out[3] = w * len;
  }
Normalize a quaternion

@param {!Float32Array} out the receiving quaternion
@param {!Float32Array} a quaternion to normalize