The WCAT W3C page https://www.w3.org/TR/vocab-dcat-2/ is based in part on the RDF serialization of the DCAT RDF https://www.w3.org/ns/dcat2.ttl.
What is the tool that is used to create the W3C pages, and where is the source kept?
They use ReSpec; that page should look familiar to the vocab landing page. Looking at the HML, it looks like they're on ReSpec 25.1.0.
You can find the ReSpec source and config here.