Piece derives Copy

mino/src/piece.rs

@@ -214,7 +214,7 @@ impl core::fmt::Debug for Cells<'_> {
 }
 
 /// Represents the current state of a piece.
-#[derive(Clone, Eq, PartialEq, Debug, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
 pub struct Piece<T> {
     /// The piece type (i.e. its shape).
     pub ty: T,