code: function getTransitionContainer(show) {
    if (document.body.scrollHeight <= window.innerHeight) {
      return lightboxTransitionContainer;
    }
  
    return document.body;
  }
docs: Gets the container to do the transition in. This is either the body
  or a fixed position container, depending on if the body has overflow
  or not.
  
  This is needed as doing the transition with position absolute can cause
  overflow, causing the scrollbars to show up during the animation.
  Depending on the OS, this can cause layout as the scrollbar shows/hides.
  
  Normally, we want to do the transition in the body, so that if the user
  scrolls while the transition is in progress (while the lightbox is)
  closing, the transition ends up in the right place.
  
  Note: you will want to prevent scrolling when the lightbox is opening
  to prevent scrolling during the animation. This will make sure the
  animation ends in the right place (and that the user does not scroll the
  body when they do not intend to).