Request: Make `engine` in `iroh_docs::protocol::Docs` public

Hello,

How feasible would it be to make the engine field of the Docs struct public? This would allow for retrieving the default author ID without async or error handling; as an alternative, perhaps the Docs struct could get a method returning a iroh_docs::engine::DefaultAuthor? I was able to do this before, but now that Docs is the protocol handler instead of Engine, I can only get the default author through the authors client, which is more of a headache because of async and Result.

Thanks!

Start by reading iroh_docs::protocol::Docs and iroh_docs::engine::DefaultAuthor, then compare the current authors-client path for retrieving the default author. Decide whether exposing engine or adding a Docs method best preserves the public API; done means callers can retrieve the default author without async or error handling.