Update array2d.pyi

include/typings/array2d.pyi

@@ -15,7 +15,7 @@ class array2d(Generic[T]):
 
     def is_valid(self, col: int, row: int) -> bool: ...
 
-    def get(self, col: int, row: int, default=None): ...
+    def get(self, col: int, row: int, default=None) -> T | None: ...
 
     @overload
     def __getitem__(self, index: tuple[int, int]) -> T: ...