Update example app (#996)

* Temporarily disable shared element screens in example app

* Fix card positioning when transitioning

example/src/app.js

 import {registerScreens} from './screens';
 registerScreens();
 
+const SHOW_SHARED_ELEMENT_SCREENS = false;
+
 const createTabs = () => {
-  let tabs = [
+  const sharedElementScreens = [
     {
       label: 'Card',
       screen: 'example.CardScreen',
       screen: 'example.ListScreen',
       icon: require('../img/list.png'),
       title: 'Shared Element Transition'
-    },
+    }
+  ];
+
+  let tabs = [
     {
       label: 'One',
       screen: 'example.FirstTabScreen',
       icon: require('../img/one.png'),
       title: 'Collapsing',
     });
+    if (SHOW_SHARED_ELEMENT_SCREENS) {
+      tabs = [...sharedElementScreens, ...tabs];
+    }
   }
   return tabs;
 };

example/src/screens/set/InformationScreen.js

   },
   imageContainer: {
     position: 'absolute',
-    top: 0
+    top: 0,
+    left: 0,
+    right: 0,
   },
   image: {
     height: 190