use new label to close stale issues (closes #815)

Author: Stephan Dilly

Diff for: .github/stale.yml

@@ -8,7 +8,7 @@ exemptLabels:
   - security
   - nostale
 # Label to use when marking an issue as stale
-staleLabel: wontfix
+staleLabel: dormant
 # 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