[CHECKLIST] Implement the mixer contract

[drewstone]

Overview

Implement the required functionality to build and test the Mixer. You can utilize the anchor contracts / mixer pallets for guidance.

• Substrate pallet implementation as an initial blueprint.
• Solidity smart contracts

Implementation

❗Note: Please add additional required fns as the implementation progresses and further investigation is conducted.

• Test deposit / withdraw on the mixer #3
• [TASK] Add events for all functions on each contract (e.g. Mixer, VAnchor) #18
• [TASK] Implement an event watcher in Rust for listening to Ink! events. #19
• Implement TX relaying functionality into the relayer for Ink! contracts #20