Document unpacked extension installation through dragging and dropping

chrome/common/extensions/docs/templates/articles/getstarted.html

 <h1>Getting Started: Building a Chrome Extension</h1>
 
 <p>
   Extensions allow you to add functionality to Chrome without diving deeply
   into native code. You can create new extensions for Chrome with those core
   technologies that you're already familiar with from web development: HTML,
   CSS, and JavaScript. If you've ever built a web page, you should feel right at
   home with extensions pretty quickly; we'll put that to the test right now by
   walking through the construction of a simple extension that will give you
   one-click access to pictures of kittens. Kittens!
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   </li>
   <li>
     <p>
       Navigate to the directory in which your extension files live, and select
       it.
     </p>
   </li>
 </ol>
 
 <p>
+  Alternatively, you can drag and drop the directory where your extension files
+  live onto <code>chrome://extensions</code> in your browser to load it.
+</p>
+
+<p>
   If the extension is valid, it'll be loaded up and active right away! If it's
   invalid, an error message will be displayed at the top of the page. Correct
   the error, and try again.
 </p>
 
 <h2 id="update-code">Fiddle with Code</h2>
 
 <p>
   Now that you've got your first extension up and running, let's fiddle with
   things so that you have an idea what your development process might look like.
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       walk you through each API in turn.
     </p>
   </li>
   <li>
     <p>
       Finally, the <a href="devguide.html">developer's guide</a> has dozens of
       additional links to pieces of documentation you might be interested in.
     </p>
   </li>
 </ul>