This diff introduces adding the Tunnelbroker client-type interface and getter in the `rust-node-addon` index file.
The purpose of the getter is to call the Tunnelbroker client class that is implemented in Rust and located in the `shared/tunnelbroker-client`.
Linear task: [[ https://linear.app/comm/issue/ENG-2613/implement-an-abstraction-for-the-redis-and-tunnelbroker-as-a-pub-sub | ENG-2613 ]]