add missing commas for better formatting

[sultanmyrza]

Hello it's great extension for flutter. There is also Flutter Gen package developed by Naver corp

I started using it but I noticed that library does not show letterSpacing when inspecting Text here is the screenshot but it has all commas in place

I will keep using Flutter extended since it support letterSpacing for text but it would be nice to

add missing commas for better formatting

Best regards,

[softmarshmallow]

This can be solved by using flutter-builder #22