Add deck card restriction info

[Sembiance]

Some of the duels decks have different restrictions as to how many cards of each rarity can be put into deck, namely: common-4, uncommon-3, rare-2, mythic/planeswalker-1.

Once I do Issue #53 I should also look into adding this 'deck card restriction' info too. Will need to figure out what it all is though. Also, maybe it doesn't belong, because the restriction may be more about the 'format' rather than the 'set'. Will need to see what my research shows when the time comes.