The names_wkdays() function produces a vector of all short weekday names
used by the bigD package.
names_wkdays()A character vector of short weekday names.
# Let's get all the short weekday names with
# the `names_wkdays()` function
names_wkdays()
#> [1] "sun" "mon" "tue" "wed" "thu" "fri" "sat"