Improve Github pages search

# Feature request

Improve the behaviour of the github pages search engine so that it presents more useful results.

## Description

As a visitor of the Github pages, I want a better search engine so that i can actually find what im looking for.

## Notes
We are currently using 'lunr' as a search engine but it does not seem to find the right things. For example searching for 'ccsh' does not show the 'CodeCharta Shell' page but searching for '(ccsh)' does. It also likes to show individual release notes on a search term. Maybe we should exclude these or add a toggle to search for them.
We could either use a different engine or try to improve the behaviour of the current one somehow.

## Acceptance criteria
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## Assumptions & Exclusions

## Development notes (optional Task Breakdown)
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## Open questions

No file, test, or entry point is named. Start by locating the GitHub Pages search implementation and its Lunr integration, then clarify the expected result ranking, release-note handling, and acceptance criteria before choosing an implementation. Done should mean the agreed search examples return useful results and are covered by tests.

Written by the indexing model from the issue text.