Adding short Fleet Automation preview callout (#31526)

* Adding short Fleet Automation preview callout

Lots of customers come to us asking for the preview, and have requested access. This page is a great place to redirect.

* Update content/en/agent/configuration/_index.md

Co-authored-by: Ursula Chen <58821586+urseberry@users.noreply.github.com>

---------

Co-authored-by: Ursula Chen <58821586+urseberry@users.noreply.github.com>

Author: ethandebnath7702

content/en/agent/configuration/_index.md

@@ -9,6 +9,10 @@ further_reading:
   text: "Agent guides"
 ---
 
+{{< callout url="https://www.datadoghq.com/product-preview/manage-agent-configurations-from-fleet-automation/" >}}
+Manage Agent configuration across your Agents centrally in Fleet Automation, at scale. To get access, complete the preview sign-up form. To set up Fleet Automation, see <a href="https://docs.datadoghq.com/agent/fleet_automation/remote_management/?tab=linux#configure-agents">configure Agents</a>.
+{{< /callout >}}
+
 This section covers information on configuring your Datadog Agents. For information on remotely configuring Datadog components, see [Remote Configuration][1]. For container installations, see [Container Monitoring][2]. For information on configuring Datadog integrations, see [Integrations][3].
 
 {{< whatsnext desc="Agent configuration documentation:" >}}
@@ -29,4 +33,4 @@ This section covers information on configuring your Datadog Agents. For informat
 
 [1]: /remote_configuration
 [2]: /containers/
-[3]: /integrations/
+[3]: /integrations/