message: security: add to Envoy security team.
diff: @@ -38,6 +38,7 @@ routing PRs, questions, etc. to the right place.
  * All maintainers
  * Piotr Sikora ([PiotrSikora](https://github.com/PiotrSikora)) (piotrsikora@google.com)
  +* Yan Avlasov ([yanavlasov](https://github.com/yanavlasov)) (yavlasov@google.com)
  # Emeritus maintainers
  