Complete spec info with the URL of the Editor's Draft

[tidoust]

One of the goals of roadmaps is to show what technologies W3C has developed or is developing in a given space. Technologies that WG are developing are those published on /TR/, and WG are still expected to publish drafts to /TR/ on a regular basis. So it makes sense to me to favor the /TR/ link when it exists.

That said, it would be useful to know the URL of the Editor's Draft (ED) of a given spec, and to have a mechanism to let roadmap authors link to the ED when they feel it's needed. We may also want to add a link to the ED in generated tables.

The URL of the ED can be retrieved from the shortname through the W3C API.

[tidoust]

Note that for published W3C specs, the https://www.w3.org/TR/[short-name]/ed/ URL now redirects to the Editor's Draft, so we don't really need to retrieve that information from the W3C API anymore. We can simply compute it.

[tidoust]

The URL of the Editor's Draft is now reported in an edDraft property. Information comes from the W3C API or from Specref, depending on the spec.