Support animation events

The event handlers look like as following

div(
  onAnimationStart --> ...,
  onAnimationonIteration --> ...,
  onAnimationEnd --> ...,
)

[raquo]

btw, forgot to mention in case anyone does something like this.

In the example above, for removeEventListener to work, you need to define your def handleAnimationEnd as a val handleAnimationEnd: js.Function1[dom.AnimationEvent, Unit] instead.

Otherwise, because addEventListener and removeEventListener accept js.Function1, this conversion from a Scala method to to js.Function1 will happen implicitly at the two usage sites of your handleAnimationEnd, and each of those conversions will create a new instance of js.Function1. So when you call removeEventListener, you will be passing a newly created instance of js.Function1 that has not been added as a listener, so the callback that was added previously will not be removed. This would become apparent if you tried to re-mount the component later, as you’d now have two callbacks registered that do the same thing twice.

Hope that makes sense. Just a small scala-js interop hiccup. When using Laminar methods (–>) you don’t have to worry about this.

[nghuuphuoc]

I am going to create the PR 👍