How to change the github repository file when adding a PR to it?

Question

GitHub

Tell me how to write an action that would add PR data to the repository file after merge to the master branch.
action.yml:

on pull_request_review:
  types:
    - submitted
  branches:
    - master
jobs:
  update-changelog:
    name: Update CHANGELOG.md
    if: ${{ github.event.review.state == 'approved' }}
    steps:
      - name: Get PR title and author
        run: ???
      - name: Add PR to log file
        run: ???