fix: update Flutter example project to use new API

fix: don't keep example project Podfile.lock in repo

thermion_flutter/thermion_flutter/lib/thermion_flutter.dart

@@ -3,4 +3,5 @@ library thermion_flutter;
 export 'thermion/thermion_flutter_plugin.dart';
 export 'thermion/widgets/thermion_widget.dart';
 export 'thermion/widgets/camera/gestures/thermion_gesture_detector.dart';
+
 export 'package:thermion_dart/thermion_dart.dart';