GH Actions: Copied stale.yml from core

Signed-off-by: Ole Herman Schumacher Elgesem <ole@northern.tech>

Author: olehermanse

.github/workflows/stale.yml

@@ -0,0 +1,24 @@
+# For more information, see:
+# https://github.com/actions/stale
+name: Label and close stale pull requests
+
+on:
+  schedule:
+    - cron: "31 19 * * *"
+  workflow_dispatch:
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+
+    steps:
+      - uses: actions/stale@v5
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          stale-pr-message: "Marking this PR as stale due to inactivity; it will be closed in 7 days."
+          stale-pr-label: "stale"
+          days-before-stale: 30
+          days-before-close: 7
+          close-pr-message: "Closing PR due to inactivity. Feel free to open a new PR if necessary."