Add note about the handwriting input attribute

Author: ericwbailey

partials/section.forms.hbs

@@ -97,6 +97,9 @@
         <li>
           <small><code translate="no">maxlength</code>'s presence is not announced by screen readers.</small>
         </li>
+        <li>
+          <small>Use <code translate="no">handwriting="true"</code> to allow handwriting input, and <code translate="no">handwriting="false"</code> to disallow it.</small>
+        </li>
       </ul>
     </fieldset>
     <!-- End of #subsection-text-input -->