Source code format

[cjng96]

Can I use the flutter source code formatter? (https://docs.flutter.dev/development/tools/formatting)

I cloned this project and made a some modification for the web platform. (I will make a pull-request it later)

But it's difficult to merge the source because I am using the VS code with the Flutter extension's source code formatter. but the original source format is not. :(

Could I make a pull-request for the code format to fit a flutter code formatter?