[Building] Save previously removed cards in a separate section

{"ops":[{"insert":"I don't know about you, but sometimes when you are building a new deck, and putting the cards into Archidekt, there are more or less cards than you had thought originally. You remove or add a few then the deck is still wrong, and you're even more confused. Having this option will let you see what cards you recently removed or edited so you can backtrack and find the issue. This feature will help make deck building easier and faster.\n"}]}