How can I add custom transitions to my Flutter route? This is my current route structure.

class MyApp extends StatelessWidget {
    // This widget is the root of your application.
    @override
    Widget build(BuildContext context) {
        return new MaterialApp(
            title: 'Yaip',
            theme: new ThemeData(
                primarySwatch: Colors.pink,
                brightness: Brightness.light
            ),
            home: new VerifyPhoneNumber(),
            routes: {
                '/verified': (BuildContext context) =>  new MobileNumberVerified(),
                '/setupprofile': (BuildContext context) =>  new SetUpProfile()
            },
        );
    }
}