Deck editor added! Plus new card interactions

Players now have the ability to customize their 12-card deck in the lobby, using any amounts of cards in the card pool.

There are now a total of 13 implemented cards, with more coming. Playtesting has been minimal, so there are likely cards I misjudged the strength of. Feel free to send feedback if a card feels to weak or strong!

Certain pieces now have static effects that give a bonus in some way when they stick on the field. One card can't move but draws you an extra card per turn!

I also added a fireball card, which lets you destroy any piece, but only at a very specific range.