[botelastic] add probot config to manage stale issues/pr

.github/ISSUE_TEMPLATE/stale.yml

@@ -0,0 +1,33 @@
+---
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 90
+
+# Number of days of inactivity before an stale issue is closed
+daysUntilClose: 30
+
+# Label to use when marking an issue as stale
+staleLabel: triage/stale
+
+issues:
+  # Comment to post when marking an issue as stale.
+  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.
+  closeComment: >
+    This issue has been automatically closed because it has not had recent
+    activity since being marked as stale.
+pulls:
+  # Comment to post when marking a PR as stale.
+  markComment: >
+    This PR 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.
+    To track this PR (even if closed), please open a corresponding issue if one
+    does not already exist.
+  # Comment to post when closing a stale PR.
+  closeComment: >
+    This PR has been automatically closed because it has not had recent
+    activity since being marked as stale.
+    Please reopen when work resumes.