Add a development sandbox to storybook

website/storybook/3-demos/Sandbox/Sandbox.js

@@ -0,0 +1,12 @@
+import React from 'react';
+import { View, StyleSheet } from 'react-native';
+
+export default class Sandbox extends React.PureComponent {
+  render() {
+    return <View styles={styles.root} />;
+  }
+}
+
+const styles = StyleSheet.create({
+  root: {}
+});

website/storybook/3-demos/Sandbox/SandboxScreen.js

@@ -0,0 +1,9 @@
+import React from 'react';
+import { storiesOf } from '../../ui-explorer';
+import Sandbox from './Sandbox';
+
+const SandboxScreen = () => <Sandbox />;
+
+if (process.env.NODE_ENV !== 'production') {
+  storiesOf('Example apps', module).add('Sandbox', SandboxScreen);
+}