[IOS] SceneDelegate에서 rootViewcontroller 변경

기존 AppDelegate에서 이런식으로 사용함.

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.rootViewController = MainViewController()
        window?.makeKeyAndVisible()
        return true
    }

xcode11 에서 멀티윈도우를 지원하기위해 SceneDelegate를 추가했다.

기존 AppDelegate에서 추가하려니 안되서 찾아보니 아래와같이 window.windowScene에 scene을 추가해주면된다.

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
        guard let scene = (scene as? UIWindowScene) else { return }
        
        
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.rootViewController = MainViewController()
        window?.windowScene = scene
        window?.makeKeyAndVisible()
    }