Hosting the rustdocs

[arpad-m]

Opening this for discussion/opinions. I'm wondering if we should host the rustdocs of the crates in this workspace somewhere (as well as their dependencies). Prior art would be the rust compiler docs.

The target audience of this would be contributors to the crates in the workspace, i.e. pageserver/proxy, etc, instead of Neon's users. IDEs provide a lot of features for code navigation, but rust documentation still fills a niche. With rust documentation of some function, you can provide a link in a discussion. If you on the other hand ran cargo doc locally, you would not be able to create links and often if you want to look something up, you are in a state where you . As the other alternative, docs.rs is great but it is always just one crate in the search index and the neon workspace is not published to crates.io, so it's not available there either.

Follow up of #4711.