Add stale bot

.github/stale.yml

@@ -0,0 +1,17 @@
+# Automatically close questions and other uncategorized issues on inactivity
+only: issues
+daysUntilStale: 30
+daysUntilClose: 7
+exemptLabels:
+  - bug
+  - enhancement
+exemptProjects: true
+exemptMilestones: true
+exemptAssignees: true
+staleLabel: 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.
+closeComment: false
+limitPerRun: 1