impl AsyncWrite for Hasher

[lightsing]

This PR introduces the implementation of the AsyncWrite trait for the Hasher struct, allowing user to read asynchronously using the Tokio library and using tokio::io::copy.

The changes include:

• Updating the Cargo.toml file to add the optional tokio feature with the necessary dependencies.
• Modifying the src/lib.rs file to implement the AsyncWrite trait for Hasher.

Please review the changes and let me know if you have any suggestions or concerns.