Update README; add guides to docs

docs/guides/react-native.md

@@ -0,0 +1,40 @@
+# React Native
+
+This is an experimental feature to support: using community-developed React
+Native components on the Web; and rendering React Native apps to Web.
+
+Use a module loader that supports package aliases (e.g., webpack), and alias
+`react-native` to `react-native-web`.
+
+```js
+// webpack.config.js
+
+module.exports = {
+  resolve: {
+    alias: {
+      'react-native': 'react-native-web'
+    }
+  }
+}
+```
+
+Web-specific implementations can use the `*.web.js` naming pattern, which
+webpack will resolve.
+
+Minor platform differences can use the `Platform` module.
+
+```js
+import { AppRegistry, Platform, StyleSheet } from 'react-native'
+
+const styles = StyleSheet.create({
+  height: (Platform.OS === 'web') ? 200 : 100
+})
+
+AppRegistry.registerComponent('MyApp', () => MyApp)
+
+if (Platform.OS === 'web') {
+  AppRegistry.runApplication('MyApp', {
+    rootTag: document.getElementById('react-root')
+  });
+}
+```