Wait for card removal method

[zhiyan114]

So currently, the code will continuously reading a card until it's removed, in some cases, this can be a really bad idea since the software may process the data multiple time if the card isnt removed "on time".

The current workaround is to record the last UID, but this breaks the edge case where user are allowed rescan their tag after removing the tag.

So is it possible to yield the loop until the reader no longer detect the card's field.