Automatically label new issues with `triage`.

.github/workflows/label-issue.yml

+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: Label issues
+on:
+  issues:
+    types:
+      - reopened
+      - opened
+jobs:
+  label_issues:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+    steps:
+      - name: Label issues
+        uses: andymckay/labeler@5c59dabdfd4dd5bd9c6e6d255b01b9d764af4414
+        with:
+          add-labels: "triage"
+          repo-token: ${{ secrets.GITHUB_TOKEN }}