Scryfall Duel Banlist wót Peavey

Adds an entry to every card on Scryfall about its legality in Duel Commander.

Checks for illegal cards (e.g. Shahrazad, Chaos Orb, gold-bordered cards etc.)
Checks for banned cards
Checks for "banned as commander" cards

It simply creates a new DOM element structure similar to those already on page, which shows the legality of the card in Duel Commander format.

Works only on English locale, cards in different languages won't be properly checked against the banlist. I might fix this some time in the future.