Add language identification swiftui demo (#729)

ios-swiftui/SherpaOnnxLangID/SherpaOnnxLangID/ContentView.swift

@@ -0,0 +1,46 @@
+//
+//  ContentView.swift
+//  SherpaOnnxLangID
+//
+//  Created by knight on 2024/4/1.
+//
+
+import SwiftUI
+
+struct ContentView: View {
+    @StateObject var viewModel = ViewModel()
+
+    var body: some View {
+        VStack {
+            Text("ASR with Next-gen Kaldi")
+                .font(.title)
+            if viewModel.status == .stop {
+                Text("See https://github.com/k2-fsa/sherpa-onnx")
+                Text("Press the Start button to run!")
+            }
+            if viewModel.status == .recording {
+                Text("Stop will show recording language.")
+            }
+            Spacer()
+            Text("Recording language is: \(viewModel.language)")
+                .frame(maxWidth: .infinity)
+            Spacer()
+            Button {
+                toggleRecorder()
+            } label: {
+                Text(viewModel.status == .stop ? "Start" : "Stop")
+            }
+        }
+        .padding()
+    }
+
+    private func toggleRecorder() {
+        Task {
+            await viewModel.toggleRecorder()
+        }
+    }
+}
+
+#Preview {
+    ContentView()
+}