Add support for additional search messages

Problem/Motivation

https://drupal.slack.com/archives/C01UHB4QG12/p1716939049039169

It would be nice if we could have better communication with the search backend (i.e. Elasticsearch on d.o, ex.g.) so that it could provide some additional information/context about your search. One example - offering a "did you mean" suggestion, so that the search backend could suggest some alternative spellings for your query. Second example - being able to add context to a specific search, for example if someone searches for "Starshot" - we could link them to a help page (because Starshot is not a "module" per se), but this might be a common use case.

Proposed resolution

Enhance the current json api to add a "header" or "search_context" key in the json that we can sanitize and display inside the Project Browser.