Checkout `jupyter-protocol`

Currently, we're relying on a C++-implementation (xeus) to communicate with the Jupyter notebook. However, ideally, we want to use our Rust libs, which we do through the classic C FFI.

Now, however, I see <https://crates.io/crates/jupyter-protocol> exists. If we're bored, we can see how much easier it would be to adopt this to get rid of the C-bindings.