While testing things for RTL support @apaskulin noticed that the Hebrew translations were not showing in search results. @bd808 explained that this was expected because our multi-lingual plugin only configures indexing for some locales.

Some experiments to determine what if anything would break if we indexed all locales have revealed multiple issues:

• Having unsupported locales in the search config causes XHR requests for the missing locales which return a 404. This in turn appears to break the initialization of the search entirely.
• "title" values in search_index.json for translated pages does not seem to be consistently translated. This may be related to T306670: Titles not translated when set in frontmatter.