Consistency of files under `./common`

As pointed out by @davidlehn here:

I see the ci workflow here comments out the comparison with the wg common files such as https://github.com/w3c/json-ld-wg/blob/main/common/terms.html. Anyone know why? That check still exists in the api repo. The idea at one point had been to update those common docs then sync here.

I don't remember and git blame does not help much. (I didn't dig into the minutes at that time though).

Note that in the RDF & SPARQL working group, we had a similar mechanism, and moved to a different solution: the common files are now hosted in a separate repo, published on GH pages, and the respec files of the spec refer to the published versions of the common files.

Start by inspecting the files under ./common and the CI workflow that comments out comparison with the JSON-LD WG common files, then review the linked json-ld-wg terms.html and the API repository's check. Read the relevant working-group minutes and respec references before deciding how consistency should be maintained; done means the chosen mechanism is documented and the common files are reliably kept in sync.