Moving DCO to workflows (opensearch-project#1458) (opensearch-project#1666)

Signed-off-by: CEHENKLE <henkle@amazon.com>

Co-authored-by: CEHENKLE <henkle@amazon.com>

Author: dblock

.github/workflows/dco.yml

@@ -0,0 +1,18 @@
+name: Developer Certificate of Origin Check
+
+on: [pull_request]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Get PR Commits
+        id: 'get-pr-commits'
+        uses: tim-actions/get-pr-commits@v1.1.0
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+      - name: DCO Check
+        uses: tim-actions/dco@v1.1.0
+        with:
+          commits: ${{ steps.get-pr-commits.outputs.commits }}