documentation: Add privacy policy for android

docs/installation/clients/sfa.md

@@ -16,3 +16,8 @@ Experimental Android client for sing-box.
 * User Agent in remote profile request is `SFA/$version ($version_code; sing-box $sing_box_version)`
 * The working directory is located at `/sdcard/Android/data/io.nekohasekai.sfa/files` (External files directory)
 * Crash logs is located in `$working_directory/stderr.log`
+
+#### Privacy policy
+
+* SFA did not collect or share personal data.
+* The data generated by the software is always on your device.

docs/installation/clients/sfa.zh.md

@@ -16,3 +16,8 @@
 * 远程配置文件请求中的 User Agent 为 `SFA/$version ($version_code; sing-box $sing_box_version)`
 * 工作目录位于 `/sdcard/Android/data/io.nekohasekai.sfa/files` (外部文件目录)
 * 崩溃日志位于 `$working_directory/stderr.log`
+
+#### 隐私政策
+
+* SFA 不收集或共享个人数据。
+* 软件生成的数据始终在您的设备上。