feat: allow multi container registry

[karbobc]

Example:

jobs:
  build:
    strategy:
      fail-fast: false
      matrix:
        platform:
          - linux/amd64
          - linux/arm64
    runs-on: ubuntu-latest
    timeout-minutes: 10
    steps:
      - uses: docker/login-action@v2
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - uses: docker/metadata-action@v4
        id: metadata
        with:
          images: |
            ${{ secrets.DOCKER_HUB_USERNAME }}/my-repo-name
            ghcr.io/${{ github.repository }}
          # avoid overwriting the latest tag because metadata-action does not add a suffix to it
          flavor: latest=false,suffix=-${{ matrix.platform }}
      - uses: docker/setup-buildx-action@v2
      - uses: docker/build-push-action@v3
        with:
          push: true
          tags: ${{ steps.metadata.outputs.tags }}
          labels: ${{ steps.metadata.outputs.labels }}
          platforms: ${{ matrix.platform }}

  build-multi-architecture:
    needs:
      - build
    runs-on: ubuntu-latest
    timeout-minutes: 10
    steps:
      - uses: docker/login-action@v2
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - uses: docker/metadata-action@v4
        id: metadata
        with:
          images: |
            ${{ secrets.DOCKER_HUB_USERNAME }}/my-repo-name
            ghcr.io/${{ github.repository }}
      - uses: int128/docker-manifest-create-action@v1
        with:
          tags: ${{ steps.metadata.outputs.tags }}
          suffixes: |
            -linux-amd64
            -linux-arm64

[int128]

Thank you for the contribution!