Update stale bot settings to exclude epics (kyma-project#105)

Author: derberg

.github/stale.yml

@@ -4,6 +4,9 @@ daysUntilStale: 60
 daysUntilClose: 7
 # Label to use when marking an issue as stale
 staleLabel: stale
+# Issues or Pull Requests with these labels will never be considered stale. Set to `[]` to disable
+exemptLabels:
+  - Epic
 # Comment to post when marking an issue as stale. Set to `false` to disable
 markComment: >
   This issue has been automatically marked as stale due to the lack of recent activity. It will soon be closed if no further activity occurs. Thank you for your contributions.