Feature Request: nix binary cache via Github Registries

[Voxelot]

Rather than using a third-party service like cachix, it would be really helpful for large open source projects to be able to use Github Registries for caching nix binaries. This would be similar to how Github currently hosts a docker registry, but instead it would allow projects to upload precompiled platform binaries to cache dependencies for their nix flakes.

Ideally, this would allow signing the cached binaries via the workflow GITHUB_TOKEN, allowing orgs to standardize the key management for their artifacts via GitHub.

The official docs for nix binary caching are found here: https://nixos.wiki/wiki/Binary_Cache