Add conditional derive of (De)Serialize to StoreId

fixes compile error with `checkpoint` feature

Author: alexkeizer

src/rt/object.rs

@@ -22,6 +22,7 @@ pub(super) struct Store<T = Entry> {
 
 
 #[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]
+#[cfg_attr(feature = "checkpoint", derive(Serialize, Deserialize))]
 pub(super) struct StoreId(usize);