Bug in add_difference() emmeans due to argument name change in the pkg

[ddsjoberg]

1. Need to update transform= to regrid=
2. add a unit test
3. bump the min version required for emmeans

tt <-
  trial %>%
  select(death, response, trt) %>%
  tbl_summary(
    by=response,
    include = -trt
  ) 

tt %>%
  add_difference(
    adj.vars = trt,
    test = everything()~"emmeans"
  )


mod <- glm(as.factor(death) ~ response_copy + trt, 
           data = trial %>% rename(response_copy = response), 
           family = stats::binomial)
emmeans::emmeans(mod, specs = ~ response_copy, regrid = "response")