What's missing is, why? It's a static site, so you won't get any real privacy about what you're reading. If you have binaries to distribute, you have other features for releasing them that let you use TLS.
That doesn't help, you can easily fingerprint a page from secondary requests or incoming/outgoing links.
The "Great Cannon".
Most of the Pages sites are just about projects themselves so the readme.md and wiki in the github repo can already serve over https and do the job just fine.