docs. sample readme

samples/simpleDemo/README.md

+# [中文版本](./README.zh.md)
+
 # Android Setup
 
 ## Prerequisites
   * Android Device
 
 ## Build
+  [More details read the doc](../../docs/ANDROID_INSTALLATION.md)
   ```bash
   adb reverse tcp:8081 tcp:8081
   adb reverse tcp:8097 tcp:8097
   npm run android
   ```
 
-
 # iOS Setup
 
 ## Prerequisites
   * Reliable iOS Device Cable
 
 ## Build
+  [More details read the doc](../../docs/IOS_INSTALLATION.md)
   ```bash
   npm install
   npm run ios

samples/simpleDemo/README.zh.md

-# [中文版本](./README.zh.md)
+# [English](./README.md)
 
-# 构建 Android APK
+# Android环境搭建
 
 ## 依赖以下环境
   * linked `react-native-agora`
   * Android Studio
   * Android SDK
-  * Reliable USB Cable
-  * Android Device
+  * 可靠的USB数据线
+  * Android 设备
 
-## Build
+## 构建步骤
+  [详情请参阅文档](../../docs/ANDROID_INSTALLATION.zh.md)
   ```bash
   adb reverse tcp:8081 tcp:8081
   adb reverse tcp:8097 tcp:8097
   npm run android
   ```
 
+# iOS环境搭建
 
-# iOS Setup
-
-## Prerequisites
-  * You should installed and linked `react-native-agora`
+## 依赖以下环境
+  * linked `react-native-agora`
   * Xcode 10.0+
-  * iOS Device
-  * Reliable iOS Device Cable
+  * iOS 设备
+  * 可靠的苹果设备数据线
 
-## Build
+## 构建步骤
+  [详情请参阅文档](../../docs/IOS_INSTALLATION.zh.md)
   ```bash
   npm install
   npm run ios

samples/simpleDemo/utils.js

-export const APPID = 'Your Agora APP_ID'; //'Your Agora APP_ID'
-export function handleError (code) {
-  let errObj = [
-    {
-      name: 'AGORA_IID_AUDIO_DEVICE_MANAGER',
-      code: 1,
-    },
-    {
-      name: 'AGORA_IID_VIDEO_DEVICE_MANAGER',
-      code: 2,
-    },
-    {
-      name: 'AGORA_IID_RTC_ENGINE_PARAMETER',
-      code: 3,
-    },
-    {
-      name: 'AGORA_IID_MEDIA_ENGINE',
-      code: 4,
-    },
-    {
-      name: 'WARN_INVALID_VIEW',
-      code: 8,
-    },
-    {
-      name: 'WARN_INIT_VIDEO',
-      code: 16,
-    },
-    {
-      name: 'WARN_PENDING',
-      code: 20,
-    },
-    {
-      name: 'ERR_JOIN_CHANNEL_REJECTED',
-      code: 17
-    },
-    {
-      name: 'ERR_START_CAMERA',
-      code: 1003
-    }
-  ];
-  
-  let found = errObj.find(e => e.code === code);
-  if (!found) {
-    throw new Error(`Code: ${code} isn't exists`);
-  }
-  return found;
-}
+export const APPID = 'Your Agora APP_ID'; //'Your Agora APP_ID'