Configuration for the stale bot (#718)

* Created the config file for the stalebot in `.github/stale.yml` to auto tag an inactive issue, and close it if still no activity.

* [stalebot] Added `exemptMilestones` and `exemptAssignees` directives

Author: hugsy

Diff for: .github/stale.yml

@@ -0,0 +1,25 @@
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 60
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 30
+# Issues with these labels will never be considered stale
+exemptLabels:
+  - pinned
+  - security
+# 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. You can
+  reopen it by adding a comment to this issue.
+# Comment to post when closing a stale issue. Set to `false` to disable
+closeComment: >
+  This issue has been automatically closed because it has not had recent activity.
+  If you are the owner of this issue, you can either re-open it and provide a more
+  complete description; or create a new issue.
+  Thank you for your contributions.
+# 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: true