Countries
The country and region list the shop supports.
Gets every country Subbly supports, with its regions. Use it to fill a country
select, and use the id of the chosen country as countryId in addresses and
in subbly.cart.getShippingMethods.
This is the full list. The countries your shop actually ships to are in
subbly.shop.shippingCountries, which has the same shape.
ReturnsPromise<Country[]>
The countries.
List the countries
Offer only the countries the shop ships to