Enable State Restoration for iOS (#647)

Author: goderbauer

experimental/veggieseasons/ios/Runner/Base.lproj/Main.storyboard

@@ -8,7 +8,7 @@
         <!--Flutter View Controller-->
         <scene sceneID="tne-QT-ifu">
             <objects>
-                <viewController id="BYZ-38-t0r" customClass="FlutterViewController" sceneMemberID="viewController">
+                <viewController restorationIdentifier="main" id="BYZ-38-t0r" customClass="FlutterViewController" sceneMemberID="viewController">
                     <layoutGuides>
                         <viewControllerLayoutGuide type="top" id="y3c-jy-aDJ"/>
                         <viewControllerLayoutGuide type="bottom" id="wfy-db-euE"/>