Debounce scroll event

[emilv]

For example: https://lodash.com/docs/4.17.4#throttle

Probably with leading and trailing both set to true.

[kiernan]

I've also found debouncing the scroll event listener to around 50ms makes it feel much smoother in Firefox at least.
Chrome on OSX for me seems to be happy either way, although I think it looks better visually without the debouncing since it handles it ok without it for me.