stale bot: ignore accepted issues

.github/stale.yml

@@ -2,6 +2,9 @@
 daysUntilStale: 30
 # Number of days of inactivity before a stale issue is closed
 daysUntilClose: 14
+# Issues with these labels will never be considered stale
+exemptLabels:
+  - accepted
 # 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