This function allows setting the default language and country settings using a valid i18n code.
Examples
# Swiss french locale
gtl_opt_set_i18n("fr_CH")
gtl_options("language")
#> [1] "fr"
gtl_options("country")
#> [1] "CH"
# American english locale
gtl_opt_set_i18n("en_US")
gtl_options("language")
#> [1] "en"
gtl_options("country")
#> [1] "US"