Scroll-linked effects warning

[bedax]

This looks like a really excellent library. I have been avoiding these sort of techniques due to the following warning that firefox gives:

This site appears to use a scroll-linked positioning effect. This may not work well with asynchronous panning; see https://developer.mozilla.org/docs/Mozilla/Performance/ScrollLinkedEffects for further details and to join the discussion on related tools and features!

It would be nice if you acknowledged this warning in the readme, saying briefly how you overcome this problem so it's clear that this isn't going to break in a few browser versions.

[alexfoxy]

I have changed the functionality to use requestAnimationFrame in the latest 1.2.0 version so this shouldn't be an issue any more.