Right now there’s no way to set these headers. statics is not really a CDN - we just pluck files out of your build and serve them so your app doesn’t have to.
S we don’t have plans to extend the statics feature now, but we’re always thinking about ways we can help people avoid having to use CDNs. 
Depending on your runtime, you may already have tools that help you cache expensive operations without resorting to another tool like a CDN. That said, it’s easy run an HTTP cache in front of your app on Fly - especially if you do not need to expire content explicitly.
Lastly, f your app can run in multiple regions, you’ll get a perf boost for both static and dynamic requests being served closer to your users.
This was a long answer to a simple question, but we’re happy to expand on any of these topics!