New scroll-position modifier

[ygongdev]

Description
Adding a new scroll-position functional modifier that mimics the native scrollTop and scrollBottom.

API

1. top
2. left

Each API will take an numerical value or a callback that exposes the element as its first argument, e.g callback(element). This allows interacting with this.element for more flexible implementation like scrollBottom or scrollRight, if needed.

Examples
1.

<div {{scroll-position top=12 left=12}}></div>

<div {{scroll-position top=this.scrollTopCallback}}></div>