Could we expose scrollToIndex ?

[FilipeCosta06]

Hi,

If I'm not mistaken, the scrollToIndex feature isn't exposed, only the scrollToId (I went a little more in details when I tried hijacking this closed Issue #46).

As I mentioned back there, I'm fearful the looping from scrollToId could cause serious performance drops and, considering Nodes already "know" their own index, and I have a reference to them, I think it couldn't hurt to expose scrollToIndex too. Also, the PropType seems to be wrong (again, I already detailed that in my comment).

I had tried simply exposing it myself by using the source code but I'm relatively knew to all this (especially React) and it was messed up bad (I think I wasn't resetting the value so scrolling etc... would become impossible AND I had another unrelated issue that I was fixing already ahah).