Possibility to reintroduce `...` to pass arguments to branching process model

As part of the full package review (#33) the dots (`...`) were removed from the simulation functions (`sim_linelist()`, `sim_outbreak()` and `sim_contacts()`), as they were not used and would warn if used (by `chkDots()`).

The dots could be added to the functions in order to pass arguments to the epidemiological simulation model used to simulate cases (currently `bpmodels::chain_sim()`). Currently it can only simulate with a Poisson offspring distribution.

The other option for this functionality is to include these parameters to toggle the simulation model within the `config`.