[wg/solid] liaise with the IETF HTTP WG

[pchampin]

The WG should ensure that the Solid Protocol is designed according best practices when it comes to Building Protocols with HTTP. An explicit liaison with the HTTP WG at IETF should therefore be mentioned in the charter.

From https://lists.w3.org/Archives/Public/public-new-work/2023Oct/0007.html

• The Solid Protocol has a copy-paste of parts of HTTP specifications, with
  modifications. Compare some of the normative statements in
  https://solidproject.org/TR/protocol with those in
  https://datatracker.ietf.org/doc/html/rfc9110. This is a bad practice
  (monkeypatching more established technical work elsewhere) that is actively
  discouraged by the IETF (see Section 2 of
  https://datatracker.ietf.org/doc/html/rfc9205) and we’d like to see this
  fixed before uplifting this kind of proposal from a CG to the scope of a
  WG. If the intent is to use HTTP, then establishing the IETF HTTP working
  group as a liaison is appropriate given this context.

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