Components: Added mention to warning progress-bar in docs

docs/components.html

@@ -1498,6 +1498,7 @@
       <ul>
         <li><code>.progress-info</code></li>
         <li><code>.progress-success</code></li>
+        <li><code>.progress-warning</code></li>
         <li><code>.progress-danger</code></li>
       </ul>
       <p>Alternatively, you can customize the LESS files and roll your own colors and sizes.</p>