ci: ensure milestone is set on PRs

Author: id

.github/workflows/pr-checks.yaml

@@ -0,0 +1,16 @@
+name: PR Checks
+
+on:
+  pull_request:
+
+jobs:
+  pr-checks:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Ensure milestone is set on the PR
+        id: check_milestone
+        run: |
+          if [ -z "${{ github.event.pull_request.milestone }}" ]; then
+            echo "No milestone set on the PR. Please set a milestone before proceeding."
+            exit 1
+          fi