Update cloudflare.md

Add additional links to relevant cloudflare documentation

Author: marleyjaffe

protocols/s3/cloudflare.md

@@ -34,4 +34,5 @@ The following features are not supported within the [open beta](https://blog.clo
 
 ## References
 
-- [Cloudflare documentation](https://developers.cloudflare.com/r2/get-started/)
+- [Cloudflare documentation](https://developers.cloudflare.com/r2/get-started/)
+- [Cloudflare API Token documentation](https://developers.cloudflare.com/r2/api/tokens/)