Support for cpt class

[rkillick]

I understand why the authors choose to support broom models but broom only covers S3 models. Changepoint models are widely used in a range of fields and practitioners often struggle to write the models down mathematically. The changepoint suite of packages fit a range of different changepoint models all built upon the cpt S4 class. I would be willing to work with the equatiomatic authors to include provision for the cpt S4 class.

[datalorax]

Hi - I appreciate the suggestion. This is not something I would personally feel comfortable implementing (I don't know the models well enough) but I'm happy to have a discussion and possibly (probably) accept a PR.

[JaySumners]

@rkillick do you have a link to a package for the cpt S4 models? I'd like to take a look.