Add rerank models and rerank API change

docs/static/llama-stack-spec.yaml

@@ -5269,6 +5269,7 @@ components:
       enum:
         - llm
         - embedding
+        - rerank
       title: ModelType
       description: >-
         Enumeration of supported model types in Llama Stack.
@@ -10182,13 +10183,16 @@ tags:
       embeddings.
 
 
-      This API provides the raw interface to the underlying models. Two kinds of models
-      are supported:
+      This API provides the raw interface to the underlying models. Three kinds of
+      models are supported:
 
       - LLM models: these models generate "raw" and "chat" (conversational) completions.
 
       - Embedding models: these models generate embeddings to be used for semantic
       search.
+
+      - Rerank models (Experimental): these models reorder the documents based on
+      their relevance to a query.
     x-displayName: Inference
   - name: Inspect
     description: >-