Update documentation

docs/installation/clients/sfi/index.md

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+# SFI
+
+Experimental official iOS client for sing-box.
+
+#### Requirements
+
+* iOS 15.0+
+* macOS 12.0+ with Apple Silicon
+
+#### Download
+
+* [TestFlight](https://testflight.apple.com/join/c6ylui2j)
+
+#### Limit
+
+* `system` tun stack not working
+
+#### Privacy policy
+
+* SFI did not collect or share personal data.
+* The data generated by the software is always on your device.

docs/installation/clients/sfi/index.zh.md

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+# SFI
+
+实验性的官方 iOS sing-box 客户端。
+
+#### 要求
+
+* iOS 15.0+
+* macOS 12.0+ with Apple Silicon
+
+#### 下载
+
+* [TestFlight](https://testflight.apple.com/join/c6ylui2j)
+
+#### 限制
+
+* `system` tun stack 不工作
+
+#### 隐私政策
+
+* SFI 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。