Feature: commit or amend to an open pull request

[reneleonhardt]

Alternatively to target_branch: it would be great to commit or amend to open pull requests in the target repo.
Cool feature would be auto-merging afterwards 😄

  # env.PR_URL for `gh pr checkout "$PR_URL"`
  pull_request: ${{github.event.pull_request.html_url}}
  # git commit --amend --no-edit --no-reset-author -- dist/*/*.js
  path_spec: "dist/*/*.js"
  # git rebase
  squash: true
  # gh pr merge --auto --merge "$PR_URL"
  auto_merge: true