Stale bot GHA (#904)

* Stale bot GHA

Signed-off-by: makhov <amakhov@mirantis.com>

* DCO check GHA. Change exempt label

Signed-off-by: makhov <amakhov@mirantis.com>

---------

Signed-off-by: makhov <amakhov@mirantis.com>

.github/workflows/stale.yml

@@ -0,0 +1,20 @@
+name: "Close stale PRs"
+on:
+  schedule:
+    - cron: "0 23 * * *"
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/stale@v9
+        with:
+          stale-issue-message: 'The issue is marked as stale since no activity has been recorded in 30 days'
+          stale-pr-message: 'The PR is marked as stale since no activity has been recorded in 30 days'
+          days-before-stale: 30
+          close-pr-label: "stale"
+          remove-issue-stale-when-updated: true
+          remove-pr-stale-when-updated: true
+          labels-to-remove-when-unstale: "stale"
+          exempt-pr-labels: "keep"
+          exempt-issue-labels: "keep"