Adds a small section and navigation link to BBQ documentation on the 'Dense vector' page

[kosabogi]

⚠️ DO NOT MERGE BEFORE elastic/elasticsearch#133066

📸 Preview

This PR introduces a new section on Better Binary Quantization (BBQ) in the Reference documentation.

In this PR, I've added a link to that newly added page.

Related issue: https://github.com/elastic/developer-docs-team/issues/333

[github-actions]

🔍 Preview links for changed docs

• solutions/search/vector/dense-vector.md

[benironside]

I am not very familiar with the topic, but this is looking readable and clear. Left a few suggestions for your consideration, hope they are helpful!

[john-wagster]

I left a few suggestions to primarily add clarity or add some gravity to certain parts of the docs, which I think can help with instilling confidence in folks who read them. Particularly worth clarifying that BBQ is default only for vectors >384 dims. Please feel free to take or leave any of it. If you have questions or concerns about BBQ or the comments I suggested don't hesitate to ask. In general the docs look good to me and I really appreciate you putting them together. thanks! lgtm

[leemthompo]

This looks great, my only concern is about splitting reference content between the "solution/use case" docs and the ES reference docs, I think most folks would prefer everything in one place.

So my one ask would be to question whether this content shouldn't live in the ES reference. I think we need to rethink how we approach this entire solution/use case section TBH.

If we're happy to have it here, we'll need to richly link from the ES reference to this content at the very least. :)

[szabosteve]

The content and the structure look great! Nice work!
Agree that it should live in ES reference, specifically under Index settings from the top of my head. We should add cross-links to this dense vector page that point to the reference material.

[szabosteve]

Thank you for the changes! LGTM!