Merge pull request httpwg#2854 from pmeenan/genart

[compression-dictionaries] Addressed feedback from Gen-ART review

Merge pull request httpwg#2844 from pmeenan/origins

[compression-dictionaries] Changed origin to reference HTTP

Fix concealed auth example

Merge pull request httpwg#2839 from nidhijaju/update-iana-reference

Add reference to RFC 8878 in IANA registry