feat: port Data.Finset.Card (#1589)

Co-authored-by: ChrisHughes24 <chrishughes24@gmail.com>

Author: Ruben-VandeVelde

Mathlib.lean

@@ -223,6 +223,7 @@ import Mathlib.Data.Fin.Fin2
 import Mathlib.Data.Fin.SuccPred
 import Mathlib.Data.Finite.Defs
 import Mathlib.Data.Finset.Basic
+import Mathlib.Data.Finset.Card
 import Mathlib.Data.Finset.Fold
 import Mathlib.Data.Finset.Image
 import Mathlib.Data.Finset.Order