Overview for each data observation type

It might be a good idea to have an overview for different model types e.g. "Continuous unbounded outcome" which would give an overview and explain differences between the model options, e.g. student t is a thicker tailed model and allows for incorporating extreme values

The issue names no files, tests, or entry points, so first identify where model-type documentation is maintained. Define the overview categories and explain how the available model options differ, including Student-t's thicker tails and treatment of extreme values; done means each requested observation type has a clear comparison.

Written by the indexing model from the issue text.