Generate a version global string in main.dart

[flowcharterappowner]

PackageInfo works for iOS and Android, but not for Web.
So until someone extends that package to include web, perhaps you could provide some functionality in your cmd line app that would, for example, add a global static variable declaration into main.dart.

That way, we wouldn't actually need to use PackageInfo to get the version info, because it would be in that global variable.