Add <caption> to Supported table markup example

docs/base-css.html

@@ -802,6 +802,7 @@ For example, <code>section</code> should be wrapped as inline.
           </table>
 <pre class="prettyprint linenums">
 &lt;table&gt;
+  &lt;caption&gt;…&lt;/caption&gt;
   &lt;thead&gt;
     &lt;tr&gt;
       &lt;th&gt;…&lt;/th&gt;

docs/templates/pages/base-css.mustache

@@ -739,6 +739,7 @@
           </table>
 <pre class="prettyprint linenums">
 &lt;table&gt;
+  &lt;caption&gt;…&lt;/caption&gt;
   &lt;thead&gt;
     &lt;tr&gt;
       &lt;th&gt;…&lt;/th&gt;