Sort present dates according to decreasing

[ryanzomorrodi]

Format dates currently sorts present dates (which are na's) always last, but this yields counter-intuitive results when decreasing = TRUE:

work <- data.frame(
  title = c("Technical Assistant", "Junior Professor", "Associate Professor"),
  location = c("Bern, Switzerland", "Bern, Switzerland", "Zürich, Switzerland"),
  start = as.Date(c("1902-01-01", "1908-01-01", "1909-01-01")),
  end = as.Date(c("1908-01-01", "1909-01-01", NA)),
  description = c("Federal Patent Office", "University of Bern", "University of Zürich")
)

work |>
  format_date(end = "end", date_format = "%Y", sort_by = "end", decreasing = TRUE) |>
  resume_entry()
#> ```{=typst}
#> #resume-entry(title: "Junior Professor",location: "Bern, Switzerland",date: "1908 - 1909",description: "University of Bern",)
#> #resume-entry(title: "Technical Assistant",location: "Bern, Switzerland",date: "1902 - 1908",description: "Federal Patent Office",)
#> #resume-entry(title: "Associate Professor",location: "Zürich, Switzerland",date: "1909 - Present",description: "University of Zürich",)
#> ```

This change sets na.last to the opposite of decreasing so present dates will be first when decreasing = TRUE and last when decreasing = FALSE

[kazuyanagimoto]

Thanks for contributing it again!