added launch in maps functionality

lib/service/url_launcher.dart

@@ -0,0 +1,8 @@
+import 'package:url_launcher/url_launcher.dart';
+
+Future<void> launchUrlFromString(String url) async {
+  final Uri uri = Uri.parse(url);
+  if (!await launchUrl(uri, mode: LaunchMode.externalApplication)) {
+    throw Exception('Could not launch $url');
+  }
+}