See:
The thing documentation for ZWave is a special script indeed.
But the solution is pretty simple.
You are able to add docs with the site posted above but finally they will end up in the ZWave binding repository, whre we will fetch all docs pages.
Binding docs: org.openhab.binding.zwave/README.md at main · openhab/org.openhab.binding.zwave · GitHub
Thing docs: org.openhab.binding.zwave/doc at main · openhab/org.openhab.binding.zwave · GitHub