api.jquery.com: add brief intro to homepage

Fixes jquery/api.jquery.com#44
Closes jquerygh-333

Author: arthurvr

themes/api.jquery.com/index.php

@@ -2,6 +2,14 @@
 <div class="content-right listing twelve columns">
 	<div id="content">
 		<h1 class="page-title">jQuery API</h1>
+		<p>jQuery is a fast, small, and feature-rich JavaScript library. It makes things like HTML document traversal and manipulation, event handling, animation, and Ajax much simpler with an easy-to-use API that works across a multitude of browsers. If you're new to jQuery, we recommend that you check out the <a href="http://learn.jquery.com/">jQuery Learning Center</a>.</p>
+		<p>If you're updating to a newer version of jQuery, be sure to read the release notes published on <a href="http://blog.jquery.com/">our blog</a>. If you're coming from a version prior 1.9, you should check out the <a href="http://jquery.com/upgrade-guide/1.9/">1.9 Upgrade Guide</a> as well.</p>
+		<p>Note that this is the API documentation for jQuery core. Other projects have API docs in other locations:</p>
+		<ul>
+			<li><a href="http://api.jqueryui.com/">jQuery UI API docs</a></li>
+			<li><a href="http://api.jquerymobile.com">jQuery Mobile API docs</a></li>
+			<li><a href="http://api.qunitjs.com">QUnit API docs</a></li>
+		</ul>
 		<hr>
 
 		<?php