NMS-13540: Highlight search terms in result page

[fooker]

This changes the version of antora-lunr-extension to our own for which implements the required functionality: https://github.com/opennms-forge/antora-lunr-extension.

To use the changes in antora-lunr-extension, the builder image has to be updated, too.
See opennms-forge/opennms-base-container#26.

In addition, a PR for upstream has been created: https://gitlab.com/antora/antora-lunr-extension/-/merge_requests/90.

[Bonrob2]

Not able to test this, but thanks for doing all the work.

[marshallmassengill]

@indigo423 this might be worth merging in but I suspect we would want to close this one and pick up something that doesn't have the conflicts.

[indigo423]

@marshallmassengill, that was an enhancement @fooker implemented to the JavaScript-based search in our docs theme. This is now 3 years old, and there is a good chance this is solved differently.

Some context: As it is today, we build the search index when the docs are built. The search is implemented in JavaScript on the client. The benefit, we don't have to deal with an external service like Agolia to manage indexing and search as a third-party. The downside is larger downloads and a bit less sophisticated search capabilities.

We have picked the simpler approach to begin with. Re-evaluating the search strategy to fit the capabilities of Antora and external search providers like Agolia could make sense. We are at least 5 years behind the capabilities of Antora and indexing services like Agolia.

[marshallmassengill]

Yeah, modernizing the docs (and in particular the search) would be a good quality of life improvement for all of our users. I'm good with a different approach but I saw this in here as I was mucking about yesterday and figured I'd suggest it since it's been out here and stale.