add CORS header example

Author: Ekwuno

content/pages/platform/functions/8_Function examples/cors-headers.md

@@ -0,0 +1,39 @@
+---
+type: example
+summary: A Pages Functions for appending CORS headers.
+tags:
+  - CORS
+pcx-content-type: configuration
+title: Adding CORS headers
+weight: 1002
+layout: example
+---
+
+
+```js
+---
+filename: /functions/_middleware.js
+---
+
+// Respond to OPTIONS method
+export const onRequestOptions: PagesFunction = async () => {
+  return new Response(null, {
+    status: 204,
+    headers: {
+      'Access-Control-Allow-Origin': '*',
+      'Access-Control-Allow-Headers': '*',
+      'Access-Control-Allow-Methods': 'GET, OPTIONS',
+      'Access-Control-Max-Age': '86400',
+    },
+  });
+};
+
+// Set CORS to all /api responses
+export const onRequest: PagesFunction = async ({ next }) => {
+  const response = await next();
+  response.headers.set('Access-Control-Allow-Origin', '*');
+  response.headers.set('Access-Control-Max-Age', '86400');
+  return response;
+};
+
+```