Expose amator's done option?

[jdgarcia]

I need to do something after the animation is done but don't see a way of doing it with the current options, outside of doing something like setTimeout using the duration time.
I noticed aminate function accepts a done option that isn't being used by this package.

[stipsan]

Yeah I plan on exposing it in some form here: #155

[stipsan]

See the Promise interface in smooth-scroll-into-view-if-needed https://github.com/stipsan/smooth-scroll-into-view-if-needed#usage