Updated readme

Author: nalejandroveron

README.md

@@ -71,6 +71,24 @@ distribution:
       - https://my-bucket.s3.amazonaws.com
 ```
 
+#### Custom header on origin
+Custom headers supports a key-value object.
+```yml
+# serverless.yml
+
+distribution:
+  component: '@serverless/aws-cloudfront'
+  inputs:
+    origins:
+      - url: https://my-assets.com
+        pathPatterns:
+          /static/images: # route any /static/images requests to https://my-assets.com
+            ttl: 10
+            allowedHttpMethods: ['GET', 'HEAD'] # optional
+            headers:
+              x-api-key: apikey # Add any custom header to be sent with the request to the origin
+```
+
 #### Custom cache behavior
 Custom cache behaviors support the same config parameters as the default cache behavior (see the example above). 
 ```yml