Updating changelog for 1.3.1 release

Author: francescoborgbonello

docs/CHANGE_LOG.md

@@ -1,6 +1,11 @@
 # Change Log
 
 ## Unreleased
+
+## 1.3.1
+
+Released on 24th January 2023
+
  - Added `is_peered_with_sentinel` monitorable for use in nodes that are running `mev-tendermint`
  - Added `node_is_peered_with_sentinel` / `validator_is_peered_with_sentinel` alerts / alerting configs
 - Updated CosmosNode `data_store`, `data_transformer`, `monitor`, and `alerter` to accomodate this new monitorable / alert