Icon notification in notification bar

[Sebastian]

I know that isn't a real issue but there are many different ways to notify if a app is running ore not. I think we should use that one who is not shown up in the notification bar ore setup a switch for hide the icon.

[Dion]

Since this is related to the bluetooth service, this probably belongs in the library repo. On android, it has already been implemented into the service. (https://github.com/ito-org/react-native-ito-bluetooth/blob/237ec890f2c483f484f02d0f8691b3ace3fe9b99/android/src/main/java/org/itoapp/strict/service/TracingService.java#L216)