Update RELEASE_NOTES.md (#44)

* Update RELEASE_NOTES.md

* Update RELEASE_NOTES.md

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Co-authored-by: Gregorius Soedharmo <arkatufus@yahoo.com>
Co-authored-by: Aaron Stannard <aaron@petabridge.com>

Author: 3 people

RELEASE_NOTES.md

@@ -1,4 +1,7 @@
+## [1.5.0] / 7 March 2023
+- Upgraded to [Akka.NET v1.5.0](https://github.com/akkadotnet/akka.net/releases/tag/1.5.0) and includes some breaking changes.
+
 ## [1.4.48] / 17 January 2023
 - Migrated from VSTest to MSTest
 - Upgraded to Akka.NET v1.4.48
-- Targeted `netstandard2.0`
+- Targeted `netstandard2.0`