Add set timeout fallback

[nigelgutzmann]

FlipMove relies on the transitionend event to know when a transition has ended, and thus call the onFinish and onFinishAll callbacks. However, in some cases, the transitionend event doesn't fire. This means that FlipMove gets into a broken state, where remainingAnimations never goes back to 0. Thus an animation will never fully complete, and FlipMove will entirely stop working.

I believe this happens when the list or element components are re-rendered really fast, and FlipMove doesn't do quite the correct reconciling to know which elements are mid-transition.

To solve this, I am taking a page out of react-bootstrap's playbook, and using setTimeout as a fallback to make sure that the transitionend event is definitely fired.

https://github.dev/react-bootstrap/dom-helpers

[nigelgutzmann]

Note: react-flip-move has discussed this approach, and has decided not to implement it: joshwcomeau#120 (comment)

I think they wanted to find the root issue leading to this bug. But that was several years ago already, and they haven't fixed it there. So for now, we can just fix it here.