Allow right-clicking on a room without selecting it

Same idea as the fix I did for spaces, we introduce a new signal called
selected instead of using ItemDelegate's button signals.

src/qml/QuickSwitcher.qml

@@ -94,7 +94,7 @@ QQC2.Dialog {
 
                 connection: root.connection
 
-                onClicked: {
+                onSelected: {
                     RoomManager.enterRoom(currentRoom);
                     root.close()
                 }