The list of two-letter ISO 3166-1 alpha-2 codes of countries, users from which will be eligible for the giveaway. If empty, then all users can participate in the giveaway. There can be up to getOption("giveaway_country_count_max") chosen countries. Users with phone number that was bought at https://fragment.com can participate in any giveaway and the country code "FT" must not be specified in the list