message: readme: add stats blog
diff: @@ -10,6 +10,7 @@ C++ L7 proxy and communication bus
  to find out more about the origin story and design philosophy of Envoy.
  * [Blog](https://medium.com/@mattklein123/envoy-threading-model-a8d44b922310) about the threading model.
  * [Blog](https://medium.com/@mattklein123/envoy-hot-restart-1d16b14555b5) about hot restart.
  +* [Blog](https://medium.com/@mattklein123/envoy-stats-b65c7f363342) about stats architecture.
  ## Related
  