Add stalebot configuration

Author: Kevin Delisle

.github/stale.yml

@@ -0,0 +1,23 @@
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 60
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 14
+# Issues with these labels will never be considered stale
+exemptLabels:
+  - pinned
+  - security
+  - critical
+  - p1
+  - major
+# Label to use when marking an issue as stale
+staleLabel: 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: >
+  This issue has been closed due to continued inactivity. Thank you for your understanding.
+  If you believe this to be in error, please contact one of the code owners,
+  listed in the `CODEOWNERS` file at the top-level of this repository.