Add additional GS3 sponsor

Author: jodygarnett

_includes/gs3-sponsors.html

@@ -27,6 +27,11 @@
        title="Deutsche Telekom"
        style="display:inline; margin-left:5px; margin-right:5px; min-width: 80px; max-width: 150px; max-height: 80px;"/> 
 </a>
+<a href="https://frachtwerk.de">
+  <img src="/sponsor/img/frachwerk-logo.svg"
+       title="Frachtwerk GmbH"
+       style="display:inline; margin-left:5px; margin-right:5px; min-width: 80px; max-width: 150px; max-height: 80px;"/> 
+</a>
 <a href="https://www.geocat.net/">
   <img src="/support/img/core-geocat.png"
        title="GeoCat BV"