ci: ensure promote command works on openvino branch

Author: jnsgruk

.github/workflows/promote-to-stable.yml

@@ -43,3 +43,21 @@ jobs:
           channel: preview/stable
           github-token: ${{ secrets.GITHUB_TOKEN }}
           store-token: ${{ secrets.SNAP_STORE_STABLE }}
+
+  promote-openvino:
+    name: ⬆️ Promote to 2.99-openvino/stable
+    environment: "2.99 OpenVino Candidate Branch"
+    runs-on: ubuntu-latest
+    if: |
+      ( !github.event.issue.pull_request )
+      && contains(github.event.comment.body, '/promote ')
+      && contains(github.event.comment.body, '2.99-openvino/stable')
+      && contains(github.event.issue.body, '2.99-openvino/stable')
+      && contains(github.event.*.labels.*.name, 'testing')
+    steps:
+      - name: ⬆️ Promote to 2.99-openvino/stable
+        uses: snapcrafters/ci/promote-to-stable@main
+        with:
+          channel: 2.99-openvino/stable
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          store-token: ${{ secrets.SNAP_STORE_STABLE }}