Adds a small section and navigation link to BBQ documentation on the 'Dense vector' page (#2575)

⚠️ DO NOT MERGE BEFORE
elastic/elasticsearch#133066

### 📸
[Preview](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2575/solutions/search/vector/dense-vector#bbq)

[This PR](elastic/elasticsearch#133066)
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: elastic/developer-docs-team#333

---------

Co-authored-by: Benjamin Ironside Goldstein <[email protected]>
Co-authored-by: John Wagster <[email protected]>
Co-authored-by: Liam Thompson <[email protected]>

Author: 4 people

solutions/search/vector/dense-vector.md

@@ -12,7 +12,7 @@ Dense neural embeddings capture semantic meaning by translating content into fix
 - Image similarity search
 - Content-based recommendations
 
-## Working with dense vectors in Elasticsearch
+## Working with dense vectors in {{es}}
 
 :::{tip}
 Using the `semantic_text` field type provides automatic model management and sensible defaults. [Learn more](../semantic-search/semantic-search-semantic-text.md).
@@ -25,4 +25,10 @@ Dense vector search requires both index configuration and a strategy for generat
     - Refer to [this overview](../semantic-search.md#using-nlp-models) of the main options
   - You can also [bring your own embeddings](bring-own-vectors.md)
     - Use the `dense_vector` field type
-2. Query the index using the [`knn` search](knn.md)
+2. Query the index using the [`knn` search](knn.md)
+
+## Better Binary Quantization (BBQ) [bbq]
+
+Better Binary Quantization (BBQ) is a vector quantization method for `dense_vector` fields that compresses vectors for faster and more memory-efficient similarity search. BBQ can improve relevance and cost efficiency, especially when used with HNSW.
+
+For details on how BBQ works, supported algorithms, and configuration examples, refer to [Better Binary Quantization (BBQ)](https://www.elastic.co/docs/reference/elasticsearch/index-settings/bbq)