chore(github): add stale bot

Author: solidnerd

.github/stale.yml

@@ -0,0 +1,18 @@
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 30
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 7
+# Issues with these labels will never be considered stale
+exemptLabels:
+  - pinned
+  - security
+  - keep-alive
+# 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
+  any activity for the last 30 days. It will be closed if no further activity
+  occurs during the next 7 days. Thank you for your contributions.
+# Comment to post when closing a stale issue. Set to `false` to disable
+closeComment: false