Created untriaged issue workflow. (opensearch-project#386)

Signed-off-by: dblock <[email protected]>

.github/workflows/add-untriaged.yml

@@ -0,0 +1,19 @@
+name: Apply 'untriaged' label during issue lifecycle
+
+on:
+  issues:
+    types: [opened, reopened, transferred]
+
+jobs:
+  apply-label:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/github-script@v6
+        with:
+          script: |
+            github.rest.issues.addLabels({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              labels: ['untriaged']
+            })