chore: automate ghcr multi-arch releases

[Eric Greer (integrii)]

Automates semver-tagged multi-arch releases for this check using GitHub Container Registry.

Parent issue: kuberhealthy/kuberhealthy#1502

Changes:

• Publish linux/amd64 and linux/arm64 images from GitHub Actions.
• Host images in GHCR as ghcr.io/kuberhealthy/:.
• Update example healthcheck YAML on main to the released GHCR image tag.
• Create or update a GitHub release when a semver tag is pushed.
• Attach release-images.txt and link the GHCR package in the release notes.
• Document the release process in RELEASE.md.

Validation:

• GitHub Actions validates multi-arch image builds on pull requests.
• Ruby YAML parse for all workflows.
• bash -n for all workflow run blocks.- git diff --check