message: fix(index): export NotificationKind
  Closes
diff: @@ -24,7 +24,7 @@ export { Subscription } from './internal/Subscription';
  export { Subscriber } from './internal/Subscriber';
  /* Notification */
  -export { Notification } from './internal/Notification';
  +export { Notification, NotificationKind } from './internal/Notification';
  /* Utils */
  export { pipe } from './internal/util/pipe';
  