added multimedia to Extras variant

variants.xml

@@ -245,6 +245,7 @@
       <group default="false">gnome-desktop</group>
       <group default="false">guest-agents</group>
       <group default="false">internet-browser</group>
+      <group default="false">multimedia</group>
       <group default="false">remote-desktop-clients</group>
     </groups>
   </variant>