chore(workflow): add stale bot (#837)

Resolves: #828
Signed-off-by: Lixia (Sylvia) Lei <lixlei@microsoft.com>

.github/workflows/stale.yml

@@ -0,0 +1,33 @@
+# Copyright The ORAS Authors.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: "Close stale issues and PRs"
+on:
+  schedule:
+    - cron: "40 10 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          stale-issue-message: "This issue is stale because it has been open for 60 days with no activity. Remove the stale label or comment to prevent it from being closed in 30 days."
+          stale-pr-message: "This PR is stale because it has been open for 45 days with no activity. Remove the stale label or comment to prevent it from being closed in 30 days."
+          close-issue-message: "This issue has been closed because there has been no activity for 30 days."
+          close-pr-message: "This PR has been closed because there has been no activity for 30 days."
+          days-before-issue-stale: 60
+          days-before-pr-stale: 45
+          days-before-issue-close: 30
+          days-before-pr-close: 30
+          exempt-all-milestones: true