[Tutorial] Example on how use `UIView.transition()` to transition views into each others.

UIApplication+SetRootController.swift

import UIKit

extension UIApplication {
  static func setRootController(_ viewController: UIViewController) {
    guard
      let scene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
      let window = scene.windows.filter({ $0.isKeyWindow }).first
    else { return }
    
    window.rootViewController = viewController
    
    UIView.transition(with: window, duration: 0.25, options: .transitionCrossDissolve, animations: nil)
  }
}