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/ContentView.swift

@@ -0,0 +1,46 @@
+//
+//  ContentView.swift
+//  SherpaOnnx
+//
+//  Created by fangjun on 2023/4/5.
+//
+
+import SwiftUI
+
+struct ContentView: View {
+    @StateObject var sherpaOnnxVM = SherpaOnnxViewModel()
+
+    var body: some View {
+        VStack {
+            Text("ASR with Next-gen Kaldi")
+                .font(.title)
+            if sherpaOnnxVM.status == .stop {
+                Text("See https://github.com/k2-fsa/sherpa-onnx")
+                Text("Press the Start button to run!")
+            }
+            ScrollView(.vertical, showsIndicators: true) {
+                HStack {
+                    Text(sherpaOnnxVM.subtitles)
+                    Spacer()
+                }
+            }
+            Spacer()
+            Button {
+                toggleRecorder()
+            } label: {
+                Text(sherpaOnnxVM.status == .stop ? "Start" : "Stop")
+            }
+        }
+        .padding()
+    }
+
+    private func toggleRecorder() {
+        sherpaOnnxVM.toggleRecorder()
+    }
+}
+
+struct ContentView_Previews: PreviewProvider {
+    static var previews: some View {
+        ContentView()
+    }
+}