只有两个slider的时候，slider切换动画不连贯

这种情况下，动画切换是第一张消失，第二张动画动画进入。而非三张以上的连贯动画切换。下面是我的初始化选项
````
{
data: banners,
dom: document.querySelector('.banner-wrap'),
isAutoplay: true,
isLooping: true,
isOverspread: true,
animateTime: 800,
duration: 5000,
oninitialized: () => {
lazyLoadImg();
}
}
````

Start by reproducing the issue with exactly two items in data and the provided autoplay, looping, animateTime, and duration options. Trace the slider transition behavior for two slides and compare it with three or more; done means the two-slide animation switches continuously rather than having the first slide disappear before the second enters.

Written by the indexing model from the issue text.