Show how to actually create and verify proofs in the user guide

[str4d]

We currently use simple-example.rs to show how to write circuits, but that file only uses the MockProver to test itself. We should have a page showing how to implement keygen, proof creation, and proof verification.

[mschoenebeck]

Any updates on this? Highly interested in this as well..

[AtHeartEngineer]

@mschoenebeck I am working on this:

https://github.com/AtHeartEngineer/halo2/blob/main/halo2_proofs/examples/e2e-example.rs https://github.com/AtHeartEngineer/halo2/blob/main/book/src/user/e2e-example.md

I'm fleshing out the documentation a bit more, but the example works.

@str4d would you mind assigning this issue to me? / Am I on the right track?

[AtHeartEngineer]

@mschoenebeck compiled e2e example documentation here: https://atheartengineer.github.io/halo2/user/e2e-example.html