[Feature] Add a method to update the README and Dockerfile without using the DH Builder

[sudo-bmitch]

Problem description

There's no obvious way to update the README and add a Dockerfile to an image built outside of Docker Hub to the UI. I can envision several ways this could be exposed to users:

1. Create a public API documented at https://docs.docker.com/docker-hub/api/latest
2. An annotation could be added to the image with a URL of the content that is automatically consumed by Hub
3. The content could be pushed separately using OCI referrers and a documented media type
4. A GitHub Action could be created that uploads it after pushing the image (least ideal since it would be GitHub specific, but would cover a large percentage of users)

docker info output

n/a

Debug Information

n/a

Error messages (on screen or in browser console)

n/a

Screenshots of the issue (if applicable)

n/a

Task List

• This is NOT a security issue
• I do NOT have a Docker subscription
• I have looked through other issues and they do NOT apply to me

[BretFisher]

Since BuildKit provenance attestations (mode=max) support adding the Dockerfile during a build, I'd think that should also be a path to showing the full Dockerfile, though that'll likely need to live per-build with the rest of the details.