Update onpr_automerge.yaml

.github/workflows/onpr_automerge.yaml

@@ -21,9 +21,24 @@ on:
       - completed
   status: {}
 jobs:
-  automerge:
-    if: ${{ (github.event.issue.pull_request) && (contains(github.event.comment.body, '/automerge')) }}    # <--- The other way to compare if it's on a PR or on an issue
+  labeler:
     runs-on: ubuntu-latest
+    steps:
+      - name: Add the automerge label
+        if: ${{ (github.event.issue.pull_request) && (contains(github.event.comment.body, '/automerge')) }}    # <--- The other way to compare if it's on a PR or on an issue
+        uses: actions/github-script@v4
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          script: |
+            github.issues.addLabels({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              labels: ['automerge']
+            })
+  automerge:
+    runs-on: ubuntu-latest
+    steps:
       - id: automerge
         name: automerge
         uses: "pascalgn/automerge-action@v0.16.2"