Add more unauthenticated labels triagebot.toml

[dev-ardi]

As an unauthorized user I can't help triage issues, not even my own. The docs say that most labels should be allowed for everyone, yet only ["bug", "invalid", "question", "enhancement"] are allowed.

[apiraino]

Do you have suggestions about which labels should not require authorization i.e. be open to everyone?

[ehuss]

The authorized labels are defined in the repository. rust-lang/rust has nearly every label authorized, see triagebot.toml. If you are working in another repository, you will need to coordinate with the maintainers there to add whichever labels are needed.