Add tag of ada-zangemann (#5976)

Reviewed-on: #5976

fsfe.org/events/2025/event-20250526-01.en.xml

@@ -19,6 +19,7 @@
             <tag key="en">
           Germany      </tag>
             <tag key="talk"/>
+        <tag key="ada-zangemann"/>
       <tag key="front-page"/>
     </tags>
   </event>