Automatically add untriaged label on issues

Sometimes when new issues are opened, they don't use the template or are
transfered in from another repo, or even are reopened when we ran triage
slightly differently.  This automation adds the `untriaged` tag if any
of these states are applied.

Coming from
opensearch-project/.github#111

Signed-off-by: Peter Nied <petern@amazon.com>

.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']
+            })