.github: configure stalebot (tendermint#91)

.github/stale.yml

@@ -0,0 +1,47 @@
+# Configuration for probot-stale - https://github.com/probot/stale
+
+# Number of days of inactivity before an Issue or Pull Request becomes stale
+daysUntilStale: 60
+
+# Number of days of inactivity before an Issue or Pull Request with the stale label is closed.
+# Set to false to disable. If disabled, issues still need to be closed manually, but will remain marked as stale.
+daysUntilClose: 9
+
+# Only issues or pull requests with all of these labels are check if stale. Defaults to `[]` (disabled)
+onlyLabels: []
+
+# Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
+exemptLabels:
+  - major-release
+
+# Set to true to ignore issues in a project (defaults to false)
+exemptProjects: true
+
+# Set to true to ignore issues in a milestone (defaults to false)
+exemptMilestones: true
+
+# Set to true to ignore issues with an assignee (defaults to false)
+exemptAssignees: false
+
+# Label to use when marking as stale
+staleLabel: stale
+
+# Comment to post when marking 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.
+
+# Limit the number of actions per hour, from 1-30. Default is 30
+limitPerRun: 30
+
+Limit to only `issues` or `pulls`
+only: pulls
+
+Optionally, specify configuration settings that are specific to just 'issues' or 'pulls':
+pulls:
+  daysUntilStale: 30
+  markComment: >
+    This pull request 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.