Add dev-dependencies as workspace dependencies

[kaimen-sano]

There is currently no way to implement dev-dependencies in a Cargo.toml that defines a workspace. this page outlines the current allowed sections.

[kerber0x]

@kaimen-sano It is possible, see https://doc.rust-lang.org/cargo/reference/workspaces.html#the-dependencies-table.

So you define it as a "normal" dependency under [workspace.dependencies] but then import it under [dev-dependencies]