Adds gh action to check for DNM labels

Author: frenzyfriday

.github/workflows/check-dnm-label.yml

@@ -0,0 +1,23 @@
+---
+name: Check for DNM labels
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - edited
+      - labeled
+      - unlabeled
+
+jobs:
+  check-for-DNM:
+    runs-on: ubuntu-latest
+    steps:
+
+      - name: Fail if PR is DNM
+        if: contains(github.event.pull_request.labels.*.name, 'do-not-merge/hold') || contains(github.event.pull_request.labels.*.name, 'do-not-merge/work-in-progress')
+        run: |
+          echo "This PR has a DNM label."
+          exit 1