Search feature in documentation on website is broken

[planger]

The search feature doesn't seem to work anymore on https://www.eclipse.org/glsp/documentation.

[xai]

While it might sound like okkur/syna#848, I'm not convinced that this is the actual problem.

On each search, a GET request for /index.json is issued which results in a 404 if the website is not run in the webserver root but in a subpath like in our case. So this might be even a completely different problem. As the feature worked previously, my next step would be bisecting hugo and/or syna which might be a bit time consuming.
(Edit: Typo)

[xai]

Definitely a different issue, which I reported to syna including a potential fix.