add readme about installing CA in Android

Author: codingfishman

docs-src/cn/src_doc.md

@@ -611,6 +611,14 @@ module.exports = {
 
 <img src="https://zos.alipayobjects.com/rmsportal/hVWkXHrzHmOKOtCKGUWx.png" width="500" />
 
+### 安卓系统信任CA证书
+首先和iOS类似，需要先扫描证书的二维码进行下载。然后不同的安卓系统安装证书的方式可能有所不同，但是安装的步骤是类似的，我们列举了几种类型。
+
+* 下载后的证书可以直接单击打开并安装，这种方式是最简单的，直接安装即可
+* 证书下载到指定目录后，需要从其他入口进行安装，包括：
+  * 设置 -> 安全性与位置信息 -> 加密与凭据 -> 从存储设备安装。找到你下载的证书文件，进行安装
+  * 设置 -> 安全 -> 从SD卡安装证书。找到你下载的证书文件，进行安装
+
 ### 配置iOS/Android系统代理
 
 * 代理服务器都在wifi设置中配置

docs-src/en/src_doc.md

@@ -602,6 +602,15 @@ install ：
 
 * Besides installing root CA, you have to "turn on" the certificate for web manually in *settings - general - about - Certificate Trust Settings*. Otherwire, safari will not trust the root CA generated by AnyProxy.
 
+### trust root CA in Android
+First of all, you need to download the root CA by clicking *Root CA* in web ui, and then scan the QR code.
+Installing CA in Android could be different based on the system, we list some common steps as below, but you can find the right way in you system with similar menu path.
+
+* The downloaded CA file can be directly installed by clicking, this is the easist way
+* You need to install the CA file from other menu, such as:
+  * Settings -> Security & Location > Encryption & credentials -> Install from storage, and find your CA file to install
+  * Settings -> Security -> Install from SD card, and find you CA file to install
+
 <img src="https://zos.alipayobjects.com/rmsportal/hVWkXHrzHmOKOtCKGUWx.png" width="500" />
 
 ### config iOS/Android proxy server