This adds a definition about how to display a moderators to the MCATE config. A moderator is any variable that you want to view information about CATEs with respect to.
add_moderator(hte_cfg, model_type, ..., .model_arguments = NULL)
HTE_cfg object to update.
Character indicating the model type for these moderators.
Currently two model types are supported:
"Stratified" for discrete moderators
"KernelSmooth" for continuous ones.
The (unquoted) names of the moderator variables.
A named list from argument name to value to pass into the
constructor for the model. See
KernelSmooth_cfg for more details.