Add appendix "Informative references" to published spec documents

[Bellangelo]

Closes #3740

This PR parses every link that is not local and is not an formative RFC using the format that the Respec expects. See https://respec.org/docs/#:~:text=ReSpec%20uses%20the%20context%20of,reference%20is%20treated%20as%20normative.

It achieves it by using the localBiblio feature of the Respec. Although, its usage is discouraged I couldn't find any other native way of adding a Informative list. Also, it is only discouraged to force you to apply your references to their free database.

You can check its result here: https://codebeautify.org/htmlviewer/y247136c8

A few notes

1. path.id is appearing as a link is fixed in another PR
2. The first entry in the list ( 1.2 ) is basically the referenced version in the YAML spec. We could change the url's text to contain more data so it would be more user friendly. For example, YAML-Version-12.
3. You might have noticed that all references have their spaces replaced with dashes. This is because the Respec does not allow spaces in the references.
4. After this PR is merged we might need to change how we handle the formative links since we will have 2 places where we handle links.

[handrews]

@Bellangelo thanks, this is a really great step forward! It also highlights some of the concerns I raised in #3785 just an hour or two before you submitted this, which is that we're really inconsistent with linking citations. Which explains why the rendered result thinks "GET" and "HEAD" are informative references (they're really just subsection links to normative reference RFC 7231). There are also some non-RFC references, most notably the JSON Schema drafts, which are normative.

I'm not quite sure what the next steps are here, but this really helps us figure out how to handle citations – we need to balance clarity in the text with what tools like this can extract. I suspect we'll need to make changes in both the spec and this PR to get something correct in the end. Let's see what others have to say about this PR and issue #3785 so far before trying to sort that out.

[ralfhandl]

@Bellangelo Sorry, the issue description was too fluffy, and your PR literally fixed it by adding every external link to the "Informative References", including links to the editors' Github user pages, or "deep links" to RFC sections for HTTP verbs, ...

I've sharpened the issue description to require conscious decision by the editors which links to mention in which appendix, and which continue to not mention there.

[Bellangelo]

@Bellangelo Sorry, the issue description was too fluffy, and your PR literally fixed it by adding every external link to the "Informative References", including links to the editors' Github user pages, or "deep links" to RFC sections for HTTP verbs, ...

I've sharpened the issue description to require conscious decision by the editors which links to mention in which appendix, and which continue to not mention there.

Hi @ralfhandl , so.. do we have to wait first for someone to decide which links should go there?

[handrews]

@Bellangelo would you be OK with closing this and continuing the discussion in issue #3740? It's clear that we need to sort out some things before this is ready for implementation, and it's best to do that in the issue.