Update RELEASE_NOTES.md for 1.5.13 release (#203)

Author: Arkatufus

RELEASE_NOTES.md

@@ -1,3 +1,10 @@
+#### 1.5.13 September 19 2023
+
+* [Updated Akka.NET to 1.5.13](https://github.com/akkadotnet/akka.net/releases/tag/1.5.13)
+* Dependency updates:
+  * [Update xUnit to 2.5.0](https://github.com/akkadotnet/Akka.MultiNodeTestRunner/pull/201)
+  * [Update TeamCity.ServiceMessages to 4.0.0](https://github.com/akkadotnet/Akka.MultiNodeTestRunner/pull/201)
+
 #### 1.5.8 June 15 2023
 
 * [Updated Akka.NET to 1.5.8](https://github.com/akkadotnet/akka.net/releases/tag/1.5.8) - which resolves issues with Akka.NET runtime and `Polyfill` errors.