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

[emmyoh]

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!