Zeronet [0] has implemented a decentralized website model, a Github alternative on there could be more resilient, though it does require additional client software to run. I believe the site owner can update their decentralized website with their cryptographic keys.

Perhaps WebTorrent [1] can be the basis for an in-browser implementation, along with service workers to stay cached and self-update without requiring a running host. Talk about serverless :^)

[0] https://zeronet.io/ [1] https://webtorrent.io/