[DOCS] Add links to features APIs

Author: lcawl

docs/reference/features/apis/features-apis.asciidoc

@@ -1,6 +1,12 @@
 [[features-apis]]
 == Features APIs
 
+.New API Reference
+[sidebar]
+--
+For the most up-to-date API details, refer to {api-es}/group/endpoint-features[features APIs].
+--
+
 You can use the following APIs to introspect and manage Features provided
 by Elasticsearch and Elasticsearch plugins.
 

docs/reference/features/apis/get-features-api.asciidoc

@@ -4,6 +4,12 @@
 <titleabbrev>Get features</titleabbrev>
 ++++
 
+.New API Reference
+[sidebar]
+--
+For the most up-to-date API details, refer to {api-es}/group/endpoint-features[features APIs].
+--
+
 Gets a list of features which can be included in snapshots using the
 <<create-snapshot-api-feature-states,`feature_states` field>> when creating a
 snapshot.

docs/reference/features/apis/reset-features-api.asciidoc

@@ -6,6 +6,12 @@
 
 experimental::[]
 
+.New API Reference
+[sidebar]
+--
+For the most up-to-date API details, refer to {api-es}/group/endpoint-features[features APIs].
+--
+
 Clears all of the state information stored in system indices by {es} features, including the security and machine learning indices.
 
 WARNING: Intended for development and testing use only. Do not reset features on a production cluster.