UIApplicationDelegate が適切ではない場合もある

[ykws]

ios-training/Documentation/NotificationCenter.md

Line 15 in eb99827

[UIApplicationDelegate](https://developer.apple.com/documentation/uikit/uiapplicationdelegate)

• In iOS 13 and later, use UISceneDelegate objects to respond to life-cycle events in a scene-based app.
• In iOS 12 and earlier, use the UIApplicationDelegate object to respond to life-cycle events.

https://developer.apple.com/documentation/uikit/app_and_environment/managing_your_app_s_life_cycle