metainfo: Add a developer-id

Author: ximion

data/metainfo/com.gexperts.Tilix.appdata.xml.in

@@ -58,7 +58,7 @@
   <launchable type="desktop-id">com.gexperts.Tilix.desktop</launchable>
 
   <content_rating type="oars-1.1"/>
-  <developer>
+  <developer id="com.gexperts">
     <name translate="no">Gerald Nunn</name>
   </developer>