Update README.md

Author: FoksWang

MLXSwiftChat/MLXSwiftChat/README.md

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 This SwiftUI demo showcases how to integrate MLXLLM for on-device AI text generation. The app allows users to input a prompt and receive AI-generated responses directly on their iPhone, leveraging Apple’s MLX framework.
 
 Demo Preview
-<p align="center"> <img src="" width="1000"> </p>
+<p align="center"> <img src="https://github.com/FoksWang/iOS-Code-Examples/blob/main/MLXSwiftChat/MLXSwiftChat/MLXSwiftChat.png" width="1000"> </p>
 
 ## ⚠️ Important Note
 This project can only run on a physical iPhone or iPad. MLXLLM does not support the iOS Simulator, as it requires direct access to Apple Silicon hardware for efficient on-device inference.