make cutData generic

[jack-davison]

This reformats cutData() into a generic function, and exports a load of vector methods as well as the data.frame method.

Methods are provided for POSIXCt, Date, Double, Integer, Character and Factor vectors, as well as data.frames (and anything that inherits the class, like tibbles).

Being a generic, this allows cutData() to be extended by other packages, if desired, and to be used more flexibly by users. For example:

mydata |>
  dplyr::mutate(
    month = cutData(date, "month"),
    no2_splits = cutData(no2),
    wd = cutData(wd, "wd")
  )

You could also achieve something funky like:

openairmaps::polar_data |>
  dplyr::mutate(
    no2 = cutData(no2),
    .by = site
  ) |>
  tidyr::drop_na(no2) |>
  ggplot(aes(x = no2, y = nox)) +
  geom_boxplot() +
  facet_wrap(vars(site), scales = "free_x")