code: function listenerDragLeave(el) {
    const $el = el;
    $el.addEventListener('dragleave', (e) => {
      if (e.target !== $el || !isTruelyLeave($el, e)) return;
      Dragging.setCallback($el.dragEndCallback);
      if ($el.dropConfig.remove && Dragging.el.parentNode === $el) {
        $el.removeChild(Dragging.el);
      }
    });
  }
docs: 监听拖动离开元素