[DOCS] Add data streams to count API (#58771) (#58772)

docs/reference/search/count.asciidoc

@@ -16,18 +16,19 @@ the <<search-search,search api>> works.
 [[search-count-api-request]]
 ==== {api-request-title}
 
-`GET /<index>/_count`
+`GET /<target>/_count`
 
 
 [[search-count-api-desc]]
 ==== {api-description-title}
 
 The count API allows you to execute a query and get the number of matches for 
-that query. It can be executed across one or more indices. The query can either 
+that query. The query can either 
 be provided using a simple query string as a parameter, or using the 
 <<query-dsl,Query DSL>> defined within the request body.
 
-The count API can be applied to <<search-multi-index,multiple indices>>.
+The count API supports <<multi-index,multi-target syntax>>. You can run a single
+count API search across multiple data streams and indices.
 
 The operation is broadcast across all shards. For each shard id group, a replica 
 is chosen and executed against it. This means that replicas increase the 
@@ -37,8 +38,14 @@ scalability of count.
 [[search-count-api-path-params]]
 ==== {api-path-parms-title}
 
-include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=index]
+`<target>`::
 
+(Optional, string)
+Comma-separated list or wildcard (`*`) expression of data streams, indices,
+and index aliases used to limit the search.
++
+To search all data streams and indices in a cluster, omit this parameter or use
+`_all` or `*`.
 
 [[search-count-api-query-params]]
 ==== {api-query-parms-title}