initialize_sim_params: Creates 'sim_params' object for global simulation parameters
In bcgov/epi.branch.sim: Simulates an Epidemic Outbreak with a Branching Process

This object is a list containing global simulation parameters such as the disease parameters, either directly defined or through a distribution with user-provided values. This object also contains some parameters that control the simulation itself. Many of these values are used in other functions, the major ones are linked here.

initialize_sim_params(
  R0,
  infect_dur,
  vary_trace,
  p_trace,
  p_trace_app,
  p_trace_app_comp,
  p_symp,
  dt,
  incub_params,
  generation_int_params,
  iso_delay_params,
  sec_infect_params,
  import_params,
  phys_dist_params
)

`R0`	Reproductive number of disease. Used in `draw_sec_infects_df` to determine the number of potential secondary infections from a primary case.
`infect_dur`	Duration of infection (in days). This constant value determines when a case is no longer active. It's also the length of the infectious period, unless the case is isolated. See `draw_infection_length`
`vary_trace`	Boolean to determine whether contact tracing is a constant or variable based on the number of new cases in a cluster. See `draw_traced_status`
`p_trace`	Probability that a case will be manually traced.
`p_trace_app`	Probability that a case will be a contact tracing app user.
`p_trace_app_comp`	Probability that a case would comply with contact tracing app recommendations.
`p_symp`	Probability that a case is symptomatic. Used in `draw_symptomatic_status`.
`dt`	Size of the simulation time step (in days).
`incub_params`	Parameters for distribution of incubation length. See `draw_incubation_period`.
`generation_int_params`	Parameters for distribution of generation intervals. See `draw_generation_interval`.
`iso_delay_params`	Parameters for distribution of delay to isolation. See `draw_isolation_delay_period`.
`sec_infect_params`	Parameters to model secondary infections. See `draw_sec_infects_df`
`import_params`	Parameters to model imported infections. See `generate_imported_infections`
`phys_dist_params`	Parameters to model physical (social) distancing or other interventions that reduce the potential to cause secondary infections. See `draw_contact_rate`