プルリクにマイルストーンを紐づけるのを強制する

Actionsで素朴に。

name: Check Pull Request Milestone
on:
  pull_request:
    types:
      - opened
      - milestoned
      - demilestoned
jobs:
  check-milestone:
    runs-on: ubuntu-latest

    steps:
      - name: Ensure milestone
        id: check_milestone
        run: |
          if [ -z "${{ github.event.pull_request.milestone }}" ]; then
            exit 1
          fi