Support for text representation transforms?

Hi there,

First of all, thanks for creating this amazing library - investing time and money to support it, and making it open source. I discovered it at JuliaCon 2021 and have been immediately fascinated by it.

**Question:** Is there interest in supporting text representation (e.g., using ScikitLearn terminology: CountVectorizer, TfidfVectorizer, NgramVectorizer, etc) features in FeatureTransforms.jl?

Some of them are covered in [TextAnalysis](https://github.com/JuliaText/TextAnalysis.jl) but are quite different, from the user perspective, from what anyone would expect looking at ScikitLearn. In particular, they are not "pipe-able" nor do they immediately return what is interesting for the user (i.e., do not implement the common "fit_transform" paradigm). In other words, it's quite non-trivial getting from text to input representations that can be fed to a machine learning model (e.g., MLJ, Flux, etc).

FeatureTransforms.jl seems a good place to support these transforms and, if interesting, I'd be happy to work on adding support for them.