Add change 32 to instructions

how_to/Change_32.md

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+- data: Create Refvalue container
+
+To make working with symbolic refs easier, we will create a `Refvalue` container
+to represent the value of a ref. `Refvalue` will have a property symbolic that
+will say whether it's a symbolic or a direct ref.
+
+This change is just refactoring, we will wrap every OID that is written or read
+from a ref in a `RefValue`.