I'll try and contain my derision towards serious conversations about hosting performance-sensitive content on GitHub/GitLab Pages. As explained in a separate comment, gziping _everything_ is wasting CPU.
If you just gzip from nginx, have content caching enabled (why don't you with static content?), and set a minimum size for gzipping, you have the best possible scenario and take a small hit on first requests of files until server-restart/cache-expiration.
If you just gzip from nginx, have content caching enabled (why don't you with static content?), and set a minimum size for gzipping, you have the best possible scenario and take a small hit on first requests of files until server-restart/cache-expiration.