RemoveEmoji doesn't need to be instanced

[pharan]

All of RemoveEmoji's members are methods and no fields.

In everything-is-a-class Java or C# world, this would mean you make it a static class with all static method members, and the resulting API would be like:
RemoveEmoji.clean(myString)

but Dart style guide recommends the library way, just putting all the methods outside of a class at top level:
https://dart.dev/effective-dart/design#avoid-defining-a-class-that-contains-only-static-members

This lets users include and exclude methods from it as they need, and use dart's library functionality as designed.