validate category keywords for dry-run

[Licenser]

Currently, when executing cargo release in dry-run mode it doesn't validate if the categories are accepted by crates.io. This leads to the dry-run mode reporting success while the final execution fials.

[epage]

rust-lang/cargo#4377 is Cargo's parent issue for this type of validation. Unlike cargo, we implement some of it as we have the flexibility to hard code some crates.io defaults.

Huh, not finding where the canonical list of categories is.