Get used resources of page on compile-time

I am building a PWA and need an "You are offline"-Page. I've built an endpoint at /offline with images and css and it looks good. I registered the page it in the service worker to precache the offline page and the page itself gets cached, but the associated resources like images and css not.

Now my question is how can I get a list of URLs required for the /offline page that I can use to precache it in the service worker? Or is there another way to solve this issue?

Thanks!