New I-D: Retry-Scope header field

Hi @all,

after a discussion with Martin and Roy on the scope of Retry-After [1]
I wrote a brief I-D to address that issue.

-
https://ioggstream.github.io/draft-polli-retry-scope/draft-polli-retry-scope.html

It's very short and it could even be integrated in httpbis-semantics.

Have a nice day,
R.

[1]: https://github.com/httpwg/http-core/pull/317#issuecomment-585868767