Document getTextArea

Author: marijnh

manual.html

@@ -635,6 +635,9 @@ <h2 id="api">Programming API</h2>
       <dt id="toTextArea"><code>toTextArea()</code></dt>
       <dd>Remove the editor, and restore the original textarea (with
       the editor's current content).</dd>
+
+      <dt id="getTextArea"><code>getTextArea() → textarea</code></dt>
+      <dd>Returns the textarea that the instance was based on.</dd>
     </dl>
 
     <p id="defineExtension">If you want to define extra methods in terms