Add Flutter text to speech demo (#1087)

flutter-examples/tts/lib/info.dart

@@ -0,0 +1,40 @@
+// Copyright (c)  2024  Xiaomi Corporation
+import 'package:flutter/material.dart';
+import 'package:url_launcher/url_launcher.dart';
+
+class InfoScreen extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    const double height = 20;
+    return Container(
+      child: Padding(
+        padding: const EdgeInsets.all(8.0),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: <Widget>[
+            Text('Everything is open-sourced.'),
+            SizedBox(height: height),
+            InkWell(
+              child: Text('Code: https://github.com/k2-fsa/sherpa-onnx'),
+              onTap: () => launch('https://k2-fsa.github.io/sherpa/onnx/'),
+            ),
+            SizedBox(height: height),
+            InkWell(
+              child: Text('Doc: https://k2-fsa.github.io/sherpa/onnx/'),
+              onTap: () => launch('https://k2-fsa.github.io/sherpa/onnx/'),
+            ),
+            SizedBox(height: height),
+            Text('QQ 群: 744602236'),
+            SizedBox(height: height),
+            InkWell(
+              child: Text(
+                  '微信群: https://k2-fsa.github.io/sherpa/social-groups.html'),
+              onTap: () =>
+                  launch('https://k2-fsa.github.io/sherpa/social-groups.html'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}