Add an HTML document with dark background to the dev server

This will allow us to see how highlighting features work on inverted
documents.

dev-server/templates/index.mustache

@@ -21,8 +21,9 @@
     <p>These document test typical/simple scenarios.</p>
     <ul>
       <li><a href="/document/burns">Poems and Songs of Robert Burns</a></li>
-      <li><a href="/document/doyle">The Disappearance of Lady Carfax, by Arthur Conan Doyle</a></li>
-      <li><a href="/document/tolstoy">Anna Karenina, by Leo Tolstoy</a></li>
+      <li><a href="/document/doyle"><i>The Disappearance of Lady Carfax</i>, by Arthur Conan Doyle</a></li>
+      <li><a href="/document/tolstoy"><i>Anna Karenina</i>, by Leo Tolstoy</a></li>
+      <li><a href="/document/raven"><i>The Raven</i> by Edgar Allen Poe</a> (light text on dark background)</li>
     </ul>
 
     <h3>Scenario HTML test documents</h3>