GitHub Pages build from release artefacts

[egekorkan]

Since we don't push the generated files, it would be good to have releases that have them. We should also change the github pages configuration to use the latest release instead of the index.html of the main branch.

[egekorkan]

Additionally, all the generated resources should be served via github pages. We can use the gens folder but put the index.html one layer up so that https://w3c.github.io/wot-thing-description/ redirects to index.html. The https://github.com/w3c/wot-resources/tree/main/td/next needs to be updated with new URIs.