Show Advisory DB status for each crate

[Nemo157]

We could be pulling data from https://github.com/RustSec/advisory-db and displaying it somewhere, maybe similar to the yanked warnings, to improve broadcasting of known security issues to potentially impacted users.

This might not be possible because the advisory db is maintained outside the Rust Project, unless its links through wg-secure-code make it official enough.

[jyn514]

Should this be part of docs.rs? I'd expect to see this on crates.io maybe, I don't know if it fits here.

[Nemo157]

I feel like it's more likely for someone to be looking at docs for a crate that they're already using than going to that crate's crates.io page. It's something that should probably be displayed in both locations really.

[pietroalbini]

I would avoid doing so unless crates.io also starts displaying that information.

[Nemo157]

Thinking about it more this is probably something that needs wider discussion, and really would be best to integrate in both crates.io and docs.rs, so I'll bring up docs.rs on the more upstream issue rust-secure-code/wg#16 in case that makes it to RFC at some point (and at least now we have an issue search result for "advisory" to follow 😁).