This adds a column named "any_miss" (by default) that describes whether
there are any missings in all of the variables (default), or whether any
of the specified columns, specified using variables names or dplyr verbs,
starts_with
, contains
, ends_with
, etc. By default the added column
will be called "any_miss_all", if no variables are specified, otherwise,
if variables are specified, the label will be "any_miss_vars" to indicate
that not all variables have been used to create the labels.