GHA to ensure milestone

.github/workflows/ensure-milestone-to-pull-requests.yml

@@ -0,0 +1,23 @@
+name: Check if pull request is milestoned
+on:
+  pull_request:
+    types: [opened, edited, milestoned, demilestoned]
+
+jobs:
+  check_milestone:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check milestone
+        uses: actions/github-script@v5
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          script: |
+            const { data: pullRequest } = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number
+            });
+            if (!pullRequest.milestone) {
+              throw new Error('Pull request does not have a milestone. Please add a milestone.');
+            }
+            console.log('Pull request has a milestone.');