Add releasenote for swap space monitoring

Author: seunghun1ee

releasenotes/notes/add-alerts-for-swap-availability-75e28ed7f913d1ec.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    Added two alerts (Warning and critical) that are triggered when the ratio
+    of (free_swap_sppace / total_swap_space) is below thresholds.
+    Each threshold can be modified by alterting value of
+    ``alertmanager_node_free_swap_warning_threshold_ratio`` and
+    ``alertmanager_node_free_swap_warning_threshold_ratio``.
+
+    Currently this solution has limitation of having one-size fits all policy.
+    This can cause unwanted alerts for the hosts which utilise swap heavily
+    Therefore it is recommended to tune the threshold or apply silence rules
+    for the needs.