Feature request: Add option to customizer (e.g., capitalize) country names on legend

[rempsyc]

It seems it is not currently possible to customize the country names on the legend, either by capitalization or full names.

library(ggflags)

# Capitalized country names don't work
d <- data.frame(
  x = rnorm(10), y = rnorm(10),
  country = sample(c("AR", "FR"), 10, TRUE),
  stringsAsFactors = FALSE
)
ggplot2::ggplot(d, ggplot2::aes(x = x, y = y, country = country)) +
  geom_flag() +
  scale_country()
#> Error in (function (classes, fdef, mtable) : unable to find an inherited method for function 'grobify' for signature '"NULL"'

# Lower case works
p <- ggplot2::ggplot(d, ggplot2::aes(x = x, y = y, country = tolower(country))) +
  geom_flag() +
  scale_country()
p

# Specifying legend labels is ignored
p + ggplot2::scale_fill_discrete(labels = c("AR", "FR"))

p + ggplot2::scale_color_manual(labels = c("AR", "FR"))

                        
p + ggplot2::scale_color_hue(labels = c("AR", "FR"))

^{Created on 2024-05-31 with reprex v2.1.0}