Live test system

[scarletcs]

To actually accurately test this library we need to do something like the following:

• Run fetches for live data form the Scryfall API.
• Save temporary files in which we declare e.g. const card: ScryfallCard.Any = { data }
• Run tsc --noEmit on those files to verify their integrity.

We will also want to apply the type validator from #21 in testing.