Introduction repeats possible alternative implementations

[ssstolk]

In document https://www.w3.org/TR/2019/WD-dx-prof-conneg-20191126/ , see these paragraphs in the Introduction:

The HTTP Header and URL QSA methods are defined as Functional Profiles of the Abstract Model. While this specification only describes these two Functional Profiles, it is expected that implementers will want to implement Functional Profiles of the Abstract Model for other environments, including environments that may be realized in the future.

and

While this specification only describes HTTP methods for content negotiation by profile via the HTTP Header and URL QSA Functional Profiles, it is expected that implementers will want to implement functionally equivalent profiles for other environments, some of which may be not yet realized future environments.

[rob-metalinkage]

fixed - close on next draft build

[rob-metalinkage]

#42