At most announce one new mesh user

This prevents potential notification flooding if you join a large mesh

src/zeronetavahi

                     toxuser="$(echo "$line" | awk -F ' ' '{print $1}')"
 
                     export DISPLAY=:0.0 && export XAUTHORITY=/home/$MESH_USERNAME/.Xauthority && sudo -u MESH_USERNAME /usr/bin/notify-send $"$toxuser" $"has joined the mesh" --icon=dialog-information
+                    break
                 fi
             fi
         done < "$CURRENT_USERS_FILE"