adding example prefix

docs/reference/search/search-your-data/retrievers-examples.asciidoc

@@ -153,7 +153,7 @@ GET /retrievers_example/_search
 
 [discrete]
 [[retrievers-examples-collapsing-retriever-results]]
-==== Grouping results by year with `collapse`
+==== Example: Grouping results by year with `collapse`
 
 In our result set, we have many documents with the same `year` value. We can clean this
 up using the `collapse` parameter with our retriever. This enables grouping results by
@@ -208,7 +208,7 @@ GET /retrievers_example/_search
 
 [discrete]
 [[retrievers-examples-text-similarity-reranker-on-top-of-rrf]]
-====  Rerank results of an RRF retriever
+==== Example: Rerank results of an RRF retriever
 
 Previously, we used a `text_similarity_reranker` retriever within an `rrf` retriever.
 Because retrievers support full composability, we can also rerank the results of an
@@ -263,7 +263,7 @@ GET retrievers_example/_search
 
 [discrete]
 [[retrievers-examples-rrf-ranking-on-text-similarity-reranker-results]]
-==== RRF with semantic reranker
+==== Example: RRF with semantic reranker
 
 For this example, we'll replace our semantic query with the `my-rerank-model`
 reranker we previously configured. Since this is a reranker, it needs an initial pool of
@@ -319,7 +319,7 @@ GET /retrievers_example/_search
 
 [discrete]
 [[retrievers-examples-chaining-text-similarity-reranker-retrievers]]
-==== Chaining multiple semantic rerankers
+==== Example: Chaining multiple semantic rerankers
 
 Full composability means we can chain together multiple retrievers of the same type. For instance, imagine we have a computationally expensive reranker that's specialized for AI content. We can rerank the results of a `text_similarity_reranker` using another `text_similarity_reranker` retriever. Each reranker can operate on different fields and/or use different inference services.
 
@@ -371,7 +371,7 @@ pick the top 10 results and rerank them using the more fine-grained
 
 [discrete]
 [[retrievers-examples-rrf-and-aggregations]]
-==== Combine RRF with aggregations
+==== Example: Combine RRF with aggregations
 
 Retrievers support both composability and most of the standard `_search` functionality. For instance,
 we can compute aggregations with the `rrf` retriever. When using a compound retriever,