Update index.mdx

add note that REST API usage not yet reflected in dashboard

Author: kathayl

src/content/docs/browser-rendering/rest-api/index.mdx

@@ -19,3 +19,9 @@ Use the REST API when you need a fast, simple way to perform common browser task
 Before you begin, make sure you [create a custom API Token](/fundamentals/api/get-started/create-token/) with the following permissions:
 
 - `Browser Rendering - Edit`
+
+:::note[Note]
+
+Currently, the Cloudflare dashboard displays usage metrics exclusively for the Workers Binding API method. Usage data for the REST API is not yet available in the dashboard. We are actively working on adding REST API usage metrics to the dashboard.
+
+:::