Add smoothScroll to the list of libraries on microjs.com

smoothScroll is a simple library that attaches a smooth scroll handler to every internal link in a document, so that when clicking on an internal link, the user is not jumped to the targetted area, but smoothly scrolled to it, using a ease-in-out type timing function.
I do not believe there are any smoothScroll libraries in microjs yet, and most people use jquery for this, so I do believe this has its place here.