Link to precise versions of underlying W3C specs

[clange]

So far, we use unversioned URLs to refer to the underlying W3C specifications, i.e.,

• https://www.w3.org/TR/odrl-model/ (which, at this point in time, points to https://www.w3.org/TR/2018/REC-odrl-model-20180215/, but may eventually point to a later version)
• https://www.w3.org/TR/vocab-dcat-3/ (which, at this point in time, points to https://www.w3.org/TR/2024/CR-vocab-dcat-3-20240118/, but may eventually point to a later version – not of DCAT overall, but of DCAT 3, e.g., the version of DCAT 3 that will be released as a Recommendation.

I think that, to avoid ambiguity, we should refer to the precise versions that are the latest ones at the point of releasing our specification.