Fix: delegate's methods of the subclass of NavigationStackController are not called

[takehilo]

As shown below, an instance of NavigationDelegate is set to delegate property in a subclass of NavigationStackController.

ExampleNavigationStackController: NavigationStackController {
  private let navigationDelegate: NavigationDelegate

  public override func viewDidLoad() {
    super.viewDidLoad()
    delegate = navigationDelegate
  }
}

class NavigationDelegate: NSObject, UINavigationControllerDelegate {
  func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
    // ... not called
  }

  func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
    // ... called
  }
}

However, navigationController(_:willShow:animated:) is not called, while navigationController(_:didShow:animated:) is called.

In the viewDidLoad method of NavigationStackController, an instance of PathDelegate is assigned to delegate property. At this point, an implementation check using responds(to:) is performed. However, since NavigationDelegate has not yet been set, navigationController(_:willShow:animated:) is determined to be unimplemented.

To address this, I added the missing methods to responds(to:).