Add "OptOutError" to the DOMException error names list

Closes #1168.

Author: Nick Burris

index.bs

@@ -5339,6 +5339,11 @@ over just using {{SyntaxError!!exception}} to refer to the {{DOMException}}. [[D
             <td>The request is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.</td>
             <td>—</td>
         </tr>
+        <tr>
+            <td>"<dfn id="optouterror" exception export><code>OptOutError</code></dfn>"</td>
+            <td>The user opted out of the process.</td>
+            <td>—</td>
+        </tr>
     </tbody>
 </table>