[DOCS] Add tip for Kibana Fleet APIs (#75711)

Adds a tip to direct external search users to the Kibana Fleet APIs.

Co-authored-by: James Rodewig <40268737+jrodewig@users.noreply.github.com>

docs/reference/fleet/index.asciidoc

@@ -1,5 +1,9 @@
 [role="xpack"]
 [[fleet-apis]]
+
+TIP: For the {kib} {fleet} APIs, see the
+{fleet-guide}/fleet-api-docs.html[`Fleet API Documentation`].
+
 == Fleet APIs
 
 The following APIs support {fleet}'s use of {es} as a data store for internal
@@ -10,4 +14,3 @@ agent and action data. These APIs are experimental and for internal use by
 
 // top-level
 include::get-global-checkpoints.asciidoc[]
-