function upAndDown(t) {
  if (t < 0.5) {
    return inAndOut(2 * t);
  }
  return 1 - inAndOut(2 * (t - 0.5));
}
Start slow, speed up, and at the very end slow down again.  This has the
same general behavior as {@link module:ol/easing.inAndOut}, but the final
slowdown is delayed.
@param {number} t Input between 0 and 1.
@return {number} Output between 0 and 1.
@api