Add auth-label-issues.yml (#6488)

substrate/.github/workflows/auto-label-issues.yml

+# If the author of the issues is not a contributor to the project, label
+# the issue with 'Z0-unconfirmed'
+
+name: Label New Issues
+on:
+  issues:
+    types: [opened]
+
+jobs:
+  label-new-issues:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Label drafts
+        uses: andymckay/labeler@master
+        if: github.event.issue.author_association == "NONE"
+        with:
+          add-labels: 'Z0-unconfirmed'