Mushroom implications

BUR #20162 has been approved by @nonamethanks.

create implication fly_agaric -> mushroom
create implication giant_mushroom -> mushroom
create implication shiitake -> mushroom

In order:
"A large red-capped mushroom with white spots"
"Mushrooms or other fungi that appear unrealistically large."
"An edible mushroom native to East Asia and used extensively in cooking."

Previous: topic #22693. It's never made sense that we can't search for things like mushroom personification because of technicalities like this.

The bulk update request #20162 (forum #255380) has been approved by @nonamethanks.