Add line with invalid UTF-8

tests/snapshots/output/changes.snapshot.txt

@@ -10,6 +10,7 @@ _ fn main() {
 ~         "The perimeter of the rectangle is {} pixels.",
 ~         perimeter(&rect1)
       );
++ <bat: INVALID UTF-8>
   }
   
   fn area(rectangle: &Rectangle) -> u32 {