update-prs.yml

on:
  push:
    branches:
      - master

jobs:
  update-pr:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@0.9.0
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            const prsResponse = await github.pulls.list({
              owner: context.repo.owner,
              repo: context.repo.repo,
            });

            await Promise.all(prsResponse.data.map(async (pr) => {
              return github.pulls.updateBranch({
                owner: context.repo.owner,
                repo: context.repo.repo,
                pull_number: pr.number,
              });
            }))