chore: replace stale workflow with probot

Author: EndBug

.github/stale.yml

@@ -0,0 +1,19 @@
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 20
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 5
+# Issues with these labels will never be considered stale
+exemptLabels:
+  - pinned
+  - security
+  - 'status: pinned'
+  - 'type: security'
+# Label to use when marking an issue as stale
+staleLabel: 'status: stale'
+# Comment to post when marking an issue as stale. Set to `false` to disable
+markComment: >
+  This issue has been automatically marked as stale because it has not had
+  recent activity. It will be closed if no further activity occurs. Thank you
+  for your contributions.
+# Comment to post when closing a stale issue. Set to `false` to disable
+closeComment: false