Add esql.async_query

Author: lcawl

docs/overlays/elasticsearch-openapi-overlays.yaml

@@ -391,4 +391,13 @@ actions:
         application/json:
           examples:
             indicesLegacyPutTemplateRequestExample1:
-              $ref: "../../specification/indices/put_template/indicesPutTemplateRequestExample1.yaml"
+              $ref: "../../specification/indices/put_template/indicesPutTemplateRequestExample1.yaml"
+  - target: "$.paths['/_query/async']['post']"
+    description: "Add examples for async esql query operation"
+    update:
+      requestBody: 
+        content: 
+          application/json: 
+            examples:
+              esqlAsyncQueryRequestExample1: 
+                $ref: "../../specification/esql/async_query/EsqlAsyncQueryRequestExample1.yaml"