Add SwiftUI demo project (#118)

* Commit after creating the project

* Add sherpa-onnx related files

* copy and modify files from sherpa-ncnn

* add app icon

ios-swiftui/SherpaOnnx/SherpaOnnx/Extension.swift

@@ -0,0 +1,20 @@
+//
+//  Extension.swift
+//  SherpaOnnx
+//
+//  Created by knight on 2023/4/5.
+//
+
+import AVFoundation
+
+extension AudioBuffer {
+    func array() -> [Float] {
+        return Array(UnsafeBufferPointer(self))
+    }
+}
+
+extension AVAudioPCMBuffer {
+    func array() -> [Float] {
+        return self.audioBufferList.pointee.mBuffers.array()
+    }
+}