Add mega floras to the infected tiles with infection counter over 2000

[Taranchuk]

Like if the infected site is left alone long enough it grows giant mushrooms (with constructed roof blocking sunlight) or vines thick enough they are considered walls by the game and have to cut through them

[Taranchuk]

There may be alien trees as well: https://github.com/Taranchuk/PurpleIvy/issues/14