implicate holding into between_fingers

BUR #13145 has been approved by @nonamethanks.

create implication between_fingers -> holding

between_fingers is for characters holding something

I'm mildly afraid of someone using this tag for weird handjobs or using it in a pedantic way, like for a chibi standing literally between two fingers, but I couldn't find any example like that, so I suppose we'll worry about that when it happens.

The bulk update request #13145 (forum #225596) has been approved by @nonamethanks.