[docs] add bundle and upgrade docs

docs/Upgrading.md

@@ -0,0 +1,47 @@
+---
+id: upgrading
+title: Upgrading
+layout: docs
+category: Guides
+permalink: docs/upgrading.html
+next: native-modules-ios
+---
+
+Upgrading to new versions of React Native will give you access to more APIs, views, developer tools
+and other goodies. Because React Native projects are essentially made up of an Android project, an
+iOS project and a JavaScript project, all combined under an npm package, upgrading can be rather
+tricky. But we try to make it easy for you. Here's what you need to do to upgrade from an older
+version of React Native:
+
+## 1. Upgrade the `react-native` dependency
+
+Note the latest version of the `react-native` npm package from here:
+
+* https://www.npmjs.com/package/react-native
+
+Open your `package.json` file and update the version of `react-native` under `dependencies` to the
+latest version. Now, in a terminal run:
+
+```sh
+$ npm install
+```
+
+## 2. Upgrade your project templates
+
+> NOTE: This feature is not yet available in the stable release of React Native. Stay tuned.
+
+The new npm package will likely contain updates to the files that are normally generated when you
+run `react-native init`, like the iOS and the Android sub-projects. To get these latest changes,
+run this in a terminal:
+
+```sh
+$ react-native upgrade
+```
+
+This will check your files against the latest template and perform the following:
+
+* If there is a new file in the template, it is simply created.
+* If a file in the template is identical to your file, it is skipped.
+* If a file is different in your project than the template, you will be prompted; you have options
+  to view a diff between your file and the template file, keep your file or overwrite it with the
+  template version. If you are unsure, press `h` to get a list of possible commands.