Add stale bot (#1820)

* add stale.yml for stale bot

* move stale.yml to the right directory

.github/stale.yml

@@ -0,0 +1,12 @@
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 5
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 2
+# Only issues or pull requests with all of these labels are check if stale. Defaults to `[]` (disabled)
+onlyLabels: question
+# Label to use when marking an issue as stale
+staleLabel: stale
+# Comment to post when closing a stale issue. Set to `false` to disable
+closeComment: >
+  This issue has been automatically closed due to inactivity. Feel free to comment in order to reopen
+  or ask again in our Telegram support group.