Add workflow to build and push Docker images to ghcr

[Flouse]

This workflow builds and pushes Docker images to the GitHub Container Registry (ghcr.io).

I bumped the Minimum Supported Rust Version (MSRV) because the build CI workflow threw errors:

• package lock_api v0.4.13 cannot be built because it requires rustc 1.64.0 or newer
• package parking_lot v0.12.4 cannot be built because it requires rustc 1.64 or newer
• package tokio-macros v2.5.0 cannot be built because it requires rustc 1.70 or newer

[TheBlueMatt]

What exactly is GHCR? Is it an alternative to the docker.org registry? Is it heavily used?

[TheBlueMatt]

Why do you want to bump the MSRV?

[Flouse]

See https://github.com/lightningdevkit/rapid-gossip-sync-server/actions/runs/15612712595/job/43977430065#step:5:112

updated the PR description as well.

[Flouse]

What exactly is GHCR? Is it an alternative to the docker.org registry? Is it heavily used?

GitHub Container Registry (GHCR) is an alternative to Docker Hub, hosted by GitHub.
GHCR's access control is based on gitHub repo permissions. I think it's convenient since the maintainers don't have to setup another hub.docker.com account.

The repo admin can control who can read, write, or administer GHCR packages.
See https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry

examples

• https://github.com/home-assistant/core/pkgs/container/home-assistant
• https://github.com/Flouse/rapid-gossip-sync-server/pkgs/container/rapid-gossip-sync-server