Document Ibis

[Cypher1]

Current State

Ibis has very bare bones documentation, some internal, some external.

Future work

Document Ibis' current state with Rust doc and Github Issues where there is future work to do.
Update Ibis' internal documentation to point to this documentation (hosted on Github Pages) and ensure all non-internal-only information is publicaly available.

[Cypher1]

As of the most recent pages build, Rustdoc output is available at https://project-oak.github.io/arcsjs-provable/ibis/docs/ibis/

It's very empty so far, but now documentation can be added incrementally.