fix: add missing Read/Write imports Update lib.rs

[moshderte]

Description: This PR resolves a compilation error in the canonical_serde submodule where the traits Read and Write (from std::io) were not imported. Because of this omission, any attempt to compile the file failed with messages like:

error[E0412]: cannot find type Write in this scope error[E0412]: cannot find type Read in this scope

Changes:

Added use std::io::{Read, Write}; at the top of mod canonical_serde.

No other behavior or logic has been modified—the only impact is that serde-based serialization/deserialization and CanonicalSerialize/CanonicalDeserialize implementations now compile successfully.

With these imports in place, cargo build and cargo test both pass without errors.

[CLAassistant]

All committers have signed the CLA.