add in CORS info

Author: spencerattick

src/api/public-api/index.md

@@ -49,3 +49,6 @@ By automatically revoking the exposed token, Segment helps keep your workspace s
 #### How do I enable this feature?
 This feature is automatically enabled for all workspaces on Team or Business tier plans.
 
+#### I'm getting a CORS error. What can I do?
+The Public API is meant to be used server-side only. If you're seeing a CORS error that means you're attempting to make a request to it on the front-end. Please move all Public API requests to a server.
+