title: SwiftUI - main(), Scene and WindowGroup are only available in iOS 14 or newer
body: <p>I started a <code>SwiftUI</code> project with <code>iOS 15</code> as a deployment target, I was asked to lower the version, so I changed it to iOS 13, after resolving some code compatibility issues I was left with an error at the entry point of the app <code>MyProjectApp.swift</code> saying that <code>main()</code> and <code>Scene</code> and <code>WindowGroup</code> are ONLY available for iOS 14+</p>
  <p><strong>How can I make the Entrypoint compatible with versions lower than iOS 14.x ?</strong></p>
  <p>this is this code for my Entry point</p>
  <pre><code>@main //'main()' is only available in iOS 14.0 or newer
  struct MyProjectApp: App {
          let persistenceController = PersistenceController.shared
          var body: some Scene { //'Scene' is only available in iOS 14.0 or newer
              WindowGroup { //'WindowGroup' is only available in iOS 14.0 or newer
                  ContentView()
              .environment(\.managedObjectContext, persistenceController.container.viewContext)
          }
      }
  }
  </code></pre>