New scroll-by modifier

[ygongdev]

Description
Adding a new scroll-by functional modifier that mimics the native scrollBy.

API
The arguments are chosen to closely mimc the API of the native scrollBy that supports an option dictionary. We will also introduce a boolean/promise to conditionally decide when to trigger the scrollBy.

Examples

<div {{scroll-by options=this.scrollOptions shouldScroll=this.shouldScroll}}></div>