feat(developer): Separate languages supported from languages designed for

The LANGUAGES metadata list for a keyboard nicely answers the question: for which languages is someone able to type with a keyboard? But when trying to answer: which keyboards should I recommend for a given language? That list is unhelpful. People don't want to be recommended the cameroonian azerty keyboard to type English. We need some way to answer that question for applications like Flex that want to give the user a list of suggested keyboards to download for the language they have asked for.