Update README.md (#12)

* Update README.md

* Update README.md

Author: shoumikhin

apple/ExecuTorchDemo/README.md

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+# ExecuTorch iOS Demo App
+
+This app uses the [MobileNet v3](https://pytorch.org/vision/main/models/mobilenetv3.html) model to process live camera images leveraging three different backends: [XNNPACK](https://github.com/google/XNNPACK), [Core ML](https://developer.apple.com/documentation/coreml) and [Metal Performance Shaders (MPS)](https://developer.apple.com/documentation/metalperformanceshaders) (Xcode 15+ and iOS 17+ only).
+
+Please refer to the [documentation](https://pytorch.org/executorch/main/demo-apps-ios.html) on how to build and run this app.
+
+<p align="center">
+  <img src="https://github.com/user-attachments/assets/69f4cc2c-a95e-4e01-ba4d-7e40791716c8" width="50%">
+</p>