Support workspace inheritance

[wetheredge]

Currently, inherited dependencies get ignored. For example, the blackbox and blackbox_decode crates in https://github.com/wetheredge/blackbox inherit tracing from the root, but it is missing from https://deps.rs/repo/github/wetheredge/blackbox.

Docs:

• https://doc.rust-lang.org/cargo/reference/workspaces.html#the-dependencies-table
• https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#inheriting-a-dependency-from-a-workspace

I might be able to take a stab at this in the next few days if it isn't already being worked on.

[nicoburns]

Another way to do this might be to treat workspace.dependencies as if they are their own crate (could have their own section on the website).