A GitHub Action that fails a pull request if there are any incomplete checklists in the issue body and/or comments. The action is triggered when a pull request is opened or its first comment (the main pull request message) is edited.
Create a file named .github/workflows/require-checklist.yaml (or any name in that directory) with the following content:
name: Require Checklist
on:
  pull_request:
    types: [opened, edited]
jobs:
  job1:
    runs-on: ubuntu-16.04
    steps:
      - uses: mheap/require-checklist-action@master
        with:
          requireChecklist: false # Set to true if needed
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}