Expose the version / tag that will be generated in the PR json

[stecullum]

Can you consider outputting the release version info that the PR will create in the pr json.

This opens up the opportunity to do any kind of extra file manipulation.. for example...

In a github action.. We can update the PR files with any additional infor we want for example...

   - uses: googleapis/release-please-action@v4
      id: release
      with:
        token: "${{ secrets.GITHUB_TOKEN }}"
        config-file: release-please-config.json
        manifest-file: .release-please-manifest.json

  ## we have just created a PR now modify it however we want eg.. replace the image tag in a k8s manifest
  - name: Modify pull-request files after RP
    if: steps.release.outputs.prs_created == 'true'. 
    uses: jaywcjlove/github-action-modify-file-content@main
    with:
      branch: ${{ fromJson(steps.release.outputs.pr).headBranchName }}
      body: "{{ fromJson(steps.release.outputs.pr).version }} .. **I didnt see it in json**
      path: 'deployment.yaml'

Thanks