Add Causr app to showcase

Summary:
Adding Causr app to the showcase.
It is written entirely in React Native.
Closes #12105

Differential Revision: D4482167

Pulled By: mkonicek

fbshipit-source-id: 560c9c59c899a291b6e5585ea8e511a66464d7d3

website/src/react-native/showcase.js

@@ -354,6 +354,13 @@ var featured = [
     infoLink: 'https://medium.com/@herdani/our-switch-to-react-native-f4ada19f0f3d#.ogwjzf2tw',
     infoTitle: 'Our switch to React Native',
   },
+  {
+    name: 'Causr',
+    icon: 'http://is2.mzstatic.com/image/thumb/Purple111/v4/9d/14/20/9d142015-3319-f613-2886-ad889609466a/source/175x175bb.jpg',
+    linkAppStore: 'https://itunes.apple.com/us/app/causr-business-networking/id1129819484',
+    infoLink: 'https://medium.com/causr/why-we-chose-react-native-abd7d58a18b5',
+    infoTitle: 'Why we chose React Native'
+  }
 ];
 
 /*