add_specifier: Add further specifications to variable names
In milanwiedemann/varnames: Create Consistent Variable Names for Repeated Measures

Add further specifications to variable names

add_specifier(
  var_names,
  str = "i",
  n,
  sep = "_",
  sort = c("previous", "current"),
  unlist = FALSE
)

`var_names`	List or vector of variable names created using the `create_var_names` function
`str`	String, specifying the suffix to be added after the input string from `var_names`.
`n`	Numeric, specifying the number of variables.
`sep`	String, specifying the sep between string from `var_names` and `str`.
`sort`	String, specifying whether to arrange the output based on the `"previous"` or `"current"` function.
`unlist`	Logical, specifying whether a "list" or "vector" should be returned.