docs(app-update): add docs

src/plugins/app-update.ts

@@ -6,21 +6,33 @@ import { Plugin, Cordova } from './plugin';
  * This plugin does self-update for android
  *
  * @usage
+ *
+ * You should first host an XML file on your server with the following data in it:
+ * ```xml
+ * <update>
+ *     <version>302048</version>
+ *     <name>APK Name</name>
+ *     <url>https://your-remote-api.com/YourApp.apk</url>
+ * </update>
+ * ```
+ *
+ * Then use the following code:
+ *
  * ```
  * import { AppUpdate } from 'ionic-native';
  *
- * let updateUrl = 'http://your-remote-api';
- * AppUpdate.checkAppUpdate(updateUrl)
- *   .then((something: any) => doSomething(something))
- *   .catch((error: any) => console.log(error));
+ * let updateUrl = 'http://your-remote-api.com/update.xml';
+ *
+ * AppUpdate.checkAppUpdate(updateUrl);
  * ```
+ *
+ * The plugin will compare the app version and update it automatically if the API has a newer version to install.
  */
 @Plugin({
   pluginName: 'AppUpdate',
   plugin: 'cordova-plugin-app-update',
   pluginRef: 'AppUpdate',
   repo: 'https://github.com/vaenow/cordova-plugin-app-update',
-  install: 'ionic plugin add cordova-plugin-app-update --save',
   platforms: ['Android']
 })
 export class AppUpdate {