Lazy-loading & SEO for hidden carousel elements

Hi folks! Thanks for maintaining this port!

So, I am using this in a server rendered context to show a list of clickable cards. Now with Lazy loading, it doesn't create those components on initialization which would affect SEO for the page since those card links aren't discoverable.

Is there any way to have SEO not suffer in such a case? If not, would you consider adding a `placeholder` prop which renders a placeholder component for lazy loading cases?

If we do that, I imagine line 113 below would need to change to instead render the placeholder component:
https://github.com/akiran/react-slick/blob/48c93ed36cfb58991e6bf4d34a1a588094281d12/src/track.js#L106-L114