add link between epichains and epidemics about ebola model

In [challenge ebola](https://epiverse-trace.github.io/tutorials-late/model-choices.html#challenge-ebola-outbreak-analysis)
> You have been tasked to generate initial trajectories of an Ebola outbreak in Guinea. Using `model_ebola()` and the the information detailed below, complete the following tasks:

We should also add a note to align with the {epichains} episodes, which models Ebola using a branching process (in practice, the two outputs are probably quite similar, but presumably the {epidemics} model doesn't include overdispersion, but can handle herd immunity if large epidemic occurs?)

_Originally posted by @adamkucharski in https://github.com/epiverse-trace/tutorials-late/pull/34#discussion_r1585103033_