Add updated Norwegian translation credits to about.html

Signed-off-by: Jeroen van Rijn <jvrnix@gmail.com>

www/templates/maposmatic/about.html

@@ -191,6 +191,8 @@ us:{% endblocktrans %}
       <li>Łukasz Jernaś ({%trans "polish translation" %})</li>
       <li>Jeff Haack ({%trans "indonesian translation" %})</li>
       <li>Hans F. Nordhaug ({%trans "norvegian bokmål translation" %})</li>
+      <li>Guttorm Flatabø ({%trans "norvegian bokmål translation" %},
+          {%trans "norvegian nynorsk translation" %})</li> 
       <li>Sylvain Collilieux ({%trans "printable stylesheet" %})</li>
     </ul>
   </td>