Support "mirrors" array in the config file for link sharing

For issue #642

src/components/roomInfoMixin.js

@@ -16,6 +16,7 @@ export default {
       isRoomTopicEditMode: false,
       roomTopicErrorMessage: null,
       messageRetentionDisplay: "",
+      currentMirror: null,
     };
   },
   mounted() {
@@ -69,7 +70,8 @@ export default {
           this.room.name,
           utils.roomDisplayTypeToQueryParam(this.room, this.roomDisplayType),
           this.roomDisplayType == ROOM_TYPE_CHANNEL, /* Auto join for channels */
-          this.roomJoinRule == "knock"
+          this.roomJoinRule == "knock",
+          this.currentMirror
         );
       }
       return null;