This function wraps gtsummary::add_stat() to calculate and display
case fatality rates (deaths among cases) with 95% confidence intervals,
using the epitabulate::case_fatality_rate_df() function internally.
add_cfr(gts_object, deaths_var)A gtsummary object created with functions such as
gtsummary::tbl_summary() or gtsummary::tbl_cross().
A logical variable name in the data indicating death
status (e.g. TRUE for death).
A modified gtsummary object with additional columns showing the number of deaths, number of cases, case fatality rate, and 95% confidence interval.