Add stale bot (#3991)

Add stale bot

.github/stale.yml

@@ -0,0 +1,21 @@
+# Number of days of inactivity before an issue becomes stale
+daysUntilStale: 28
+# Number of days of inactivity before a stale issue is closed
+daysUntilClose: 14
+# Issues with these labels will never be considered stale
+exemptLabels:
+    - 1. developing
+    - 2. to review
+    - 3. to release
+    - approved
+    - enhancement
+    - overview
+# 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 request did not receive an update in the last 4 weeks.
+    Please take a look again and update the issue with new details,
+    otherwise the issue will be automatically closed in 2 weeks. Thank you!
+# Comment to post when closing a stale issue. Set to `false` to disable
+closeComment: false