Default to absolute fill for stack screen items. (#335)

This change makes navigation screen wrapper to set absolute fill style for screen items wrendered within native stack. We obvserved an issue where screens are rendered with a versy small height when the initial style is not set properly on iOS. This change makes the screen default to full screen and only then be resized down in case navigation bars are set.

createNativeStackNavigator.js

@@ -204,7 +204,7 @@ class StackView extends React.Component {
     return (
       <Screen
         key={`screen_${route.key}`}
-        style={options.cardStyle}
+        style={[StyleSheet.absoluteFill, options.cardStyle]}
         stackAnimation={stackAnimation}
         stackPresentation={stackPresentation}
         gestureEnabled={