clean_fit_dt: Format fit data.table
In evanjflack/cfo.behavioral: Behavioral Hazard and Patient Decision Making

Format the estimates, standard errors, and significance stars for estimate tables to be printed in Latex.

clean_fit_dt(
  dt,
  id_vars,
  est_var = "estimate",
  se_var = "std.error",
  p_var = "p.value",
  dig = 3
)

`dt`	data.table
`id_vars`	character vector, name(s) of the idifiying featues of the estimate
`est_var`	character, name of the estimate column
`se_var`	character, name pf the standard error coulumn
`p_var`	character, name of the value column
`dig`	integer, number of significant features to round estimate and standard error