docs: chat recall tutorial (#5975)

documentation/src/components/PlatformExtensionNote.js

@@ -0,0 +1,11 @@
+import React from "react";
+import Admonition from '@theme/Admonition';
+
+export const PlatformExtensionNote = () => {
+  
+  return (
+    <Admonition type="info" title="Platform Extension">
+       <p>This is a <a href="/goose/docs/getting-started/using-extensions#built-in-platform-extensions">built-in platform extension</a> that's enabled by default. Platform extensions provide core functionality and are used within goose just like MCP server extensions.</p>
+    </Admonition>
+  );
+};