Allow to pass an Observable as notification content

It would be cool, when we can pass Observables as content for notifications. Then can something like this possible:

notificationService.show(translationService.stream('translationKey'));

Relates to:

Line 37 in f9378e0

content?: any;

Line 59 in f9378e0

    
           public async show(notification: string | WorkbenchNotificationConfig, qualifier?: Qualifier): Promise<void> {