(JMAP) [@!RFC8620] markup exposed

[saper]

(JMAP) [@!RFC8620] and [@?RFC3501] links are displayed with exposed markup and do not link to anything on https://jmap.io/spec-mail.html

(maybe this is for https://github.com/jmapio/jmap/blob/bdb932e26c0d729cbb351acde090b4903e28252a/spec/mail/message.mdown I don't know)