actions/runner-images ? reverse-engineered prompt

Build me a repo that contains everything needed to define and produce the VM images used for GitHub Actions runners, with clear docs for how to build them and how the different images are organized.

I want it to support the main runner image families like Ubuntu, macOS, Windows, and arm64 where it makes sense, and to make it easy to see what software comes on each image. Please include a simple way to update image definitions, generate release notes or image readmes, and keep track of what is supported or deprecated.

Make the documentation easy to follow for someone who is not deep into infrastructure, and add enough scripts and helpers so the build process can run from the repo without guessing. If you need to check current GitHub Actions runner image conventions or related docs online, go ahead and do that.