client/lib/scroll-into-viewport/index.js
function isInViewportRange( elementStart, elementEnd ) {
	let viewportStart = window.scrollY,
		viewportEnd = document.documentElement.clientHeight + window.scrollY;
	return elementStart > viewportStart && elementEnd < viewportEnd;
}
function isInViewportRange( elementStart, elementEnd ) {
	let viewportStart = window.scrollY,
		viewportEnd = document.documentElement.clientHeight + window.scrollY;
	return elementStart > viewportStart && elementEnd < viewportEnd;
}
Checks whether the given bounds are within the viewport
@param {number} elementStart
@param {number} elementEnd
@returns {boolean}