null safe implimentation

[Yoda-Man]

The library 'package:flutter_mobile_vision/flutter_mobile_vision.dart' is legacy, and should not be imported into a null safe library.\nTry migrating the imported library.

[xeonn]

The library 'package:flutter_mobile_vision/flutter_mobile_vision.dart' is legacy, and should not be imported into a null safe library.\nTry migrating the imported library.

I prefer this plugin than the rest due to its simplicity. I hope the owner considers migrating it to Null Safety.

[Yoda-Man]

I totally love the plugin. I will keep my fingers crossed.

Please make a pull request to https://github.com/harrowmykel/flutter_mobile_vision_2

He already migrated the plugin to non null.

https://pub.dev/packages/flutter_mobile_vision_2