Add support for the Deprecation header

[dunglas]

This a new Internet Draft that completes the Sunset that we already support: https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-deprecation-header. Implementing it should be quite easy.

(Discovered during @nfrankel's talk at Platform Summit 2023: https://github.com/nfrankel/evolve-apis/)

[nfrankel]

Happy to be of service!

[soyuka]

through HeaderParameter's this is quite easy to do we just need to document that.