`type_text()` should accept `family` argument

[grantmcdermott]

E.g.

plt(
  mpg ~ hp, mtcars,
  type = type_text(
    labels = row.names(mtcars),
    family = "HersheyScript",
    xpd = NA
  )
)

We already support fine-grained control for other text arguments like font and srt, so this would be a case of improved consistency IMO.