text: Title: [ENH] interface to `tsai` package
  Body: `tsai` is an excellent package for deep learning models for time series, mostly for time series classification, but some also for forecasting.
  https://github.com/timeseriesAI/tsai
  
  It has a unified interface to these, so it should be easy to interface these from `sktime`. Possibly, even `_DelegatedClassifier` or `_DelegatedForecaster` might be used.
  
  As a recipe, I think different classifiers should be different classes; obviously, we also want to credit the authors of the individual classifiers, with their GitHub names, in the `"authors"` tag - these can be gleaned from the commit history.
  
  FYI @oguiza, it would be great to collaborate on this! Ref issue on `tsai`: https://github.com/timeseriesAI/tsai/issues/931
  