update sms plugin

packages/flutter_sms/lib/src/user_agent/io.dart

@@ -0,0 +1,5 @@
+import 'dart:io';
+
+bool isCupertino() {
+  return Platform.isIOS || Platform.isMacOS;
+}

packages/flutter_sms/lib/src/user_agent/web.dart

@@ -0,0 +1,20 @@
+import 'package:web/web.dart' as web;
+
+bool isCupertino() {
+  final _devices = [
+    'iPad Simulator',
+    'iPhone Simulator',
+    'iPod Simulator',
+    'iPad',
+    'iPhone',
+    'iPod',
+    'Mac OS X',
+  ];
+  final String _agent = web.window.navigator.userAgent;
+  for (final device in _devices) {
+    if (_agent.contains(device)) {
+      return true;
+    }
+  }
+  return false;
+}