speedup numfmt assignment

[JanMarvin]

provides new function dataframe_to_dims().

library(openxlsx2)

beg <- "1900-1-1"
end <- "2022-11-18"

dat <- seq(
  from = as.POSIXct(beg, tz="UTC"),
  to   = as.POSIXct(end, tz="UTC"),
  by   = "day"
)

out <- data.frame(
  date = dat,
  chr  = as.character(dat),
  num  = seq_along(dat)-1
)

# huge improvement
wb <- wb_workbook() %>% 
  wb_add_worksheet() %>%
  wb_add_data(x = out) %>% 
  wb_add_numfmt(dims = "C1:C44882", numfmt = "#.0") %>% 
  wb_open()