fix(iterators5): derive Clone, Copy

To allow more flexibility in solutions, derive `Clone` and `Copy`
for `Progress`.

exercises/standard_library_types/iterators5.rs

@@ -15,7 +15,7 @@
 
 use std::collections::HashMap;
 
-#[derive(PartialEq, Eq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
 enum Progress {
     None,
     Some,