Support multi-user login

[a76yyyy]

Behaviour

Currently it seems to support only a single user login to a hub address, hope to support multi-user login

Steps to reproduce this issue

- name: a Login to DockerHub
  uses: docker/login-action@v2
  with:
    registry: docker.io
    username: ${{ secrets.A_DOCKER_USERNAME }}
    password: ${{ secrets.A_DOCKER_PASSWORD }}
- name: b login to DockerHub
  uses: docker/login-action@v2
  with:
    registry: docker.io
    username: ${{ secrets.b_DOCKER_USERNAME }}
    password: ${{ secrets.b_DOCKER_PASSWORD }}

Expected behaviour

Support multi-user login

# cat ~/.docker/config.json

{
    "auths":{
        "https://index.docker.io/v1/":{
            "auth":"xxxx"
        },
        "https://index.docker.io/v1/":{
            "auth":"xxxx"
        }
    }
}

Actual behaviour

# cat ~/.docker/config.json

{
    "auths":{
        "https://index.docker.io/v1/":{
            "auth":"xxxx"
        }
    }
}

[crazy-max]

Multi-auth for the same registry is not supported by the docker cli. Suggest to open an issue on https://github.com/docker/cli instead.