get_feature_names_out for encoders

[CarloLepelaars]

I would be happy to implement get_feature_names_out for all the Embetter objects. I will implement them by just adding a new method (without a Mixin).

[koaning]

I might want to put that on hold for a bit, partially because I don't have a super clear roadmap in what I do/not want to cover in this library. Maybe I want to have sparse embeddings, or 2d/3d embeddings as well? In which case I might have tools that are a bit of an anti-pattern.

Maybe later, but at this point the project needs to mature before I consider such features.