Add basic flavors

lib/main_dev.dart

@@ -0,0 +1,8 @@
+import 'package:flutter/widgets.dart';
+import 'package:hiddify/bootstrap.dart';
+import 'package:hiddify/domain/environment.dart';
+
+void main() async {
+  final widgetsBinding = WidgetsFlutterBinding.ensureInitialized();
+  return lazyBootstrap(widgetsBinding, Environment.dev);
+}