ct_countries_table: Extract country code look up table from UN Comtrade
Description
Returns a dataframe of countries and country codes,
downloaded from UN Comtrade. For use with the UN Comtrade API, full API
docs can be found at https://comtrade.un.org/data/doc/api/
Default value NULL, otherwise this should be a url as a
char string that points to the reporter areas JSON dataset on the Comtrade
website. Only necessary if the Comtrade site changes from
https://comtrade.un.org/data/cache/reporterAreas.json
partners
Default value NULL, otherwise this should be a url as a
char string that points to the reporter areas JSON dataset on the Comtrade
website. Only necessary if the Comtrade site changes from
https://comtrade.un.org/data/cache/partnerAreas.json
Value
A dataframe of countries and country codes, downloaded from UN
Comtrade.