Feature request: Add support of slick slide change events and lazy loading images

[niki4810]

@kenwheeler as per our discussion, creating this ticket for adding support for

• carousel events like on slide change, before slide change.
• data-lazy functionality for lazy loading images with in slick carousel

Thanks, Nikhilesh

[jherr]

:+1:

[aij]

I have a slightly different use case for lazy loading: We're rendering thousands of slides and -- for performance -- would like to avoid even creating DOM elements for all the slides that will not be visible anyway.

Currently, we're using react-slick but it is sluggish and the lazyLoad option is iffy...