Load user preferences at start of app. Manage locations: user is able to add locations by lat and lon to shared preferences

lib/main.dart

@@ -1,8 +1,13 @@
 import 'package:flutter/material.dart';
 import 'package:wetter/components/main_menu.dart';
 import 'package:wetter/screens/main_weather_view.dart';
+import 'package:wetter/services/user_preferences.dart';
 
-void main() => runApp(const MyApp());
+void main() async {
+  WidgetsFlutterBinding.ensureInitialized();
+  await UserPreferences.init();
+  runApp(const MyApp());
+}
 
 class MyApp extends StatefulWidget {
   const MyApp({super.key});