update changelog.md

Author: alexsohn1126

CHANGELOG.md

@@ -13,6 +13,7 @@
 - The SDK now makes use of the new SessionEndStatus `Unhandled` when capturing an unhandled but non-terminal exception, i.e. through the UnobservedTaskExceptionIntegration ([#4633](https://github.com/getsentry/sentry-dotnet/pull/4633), [#4653](https://github.com/getsentry/sentry-dotnet/pull/4653))
 - The SDK now provides a `IsSessionActive` to allow checking the session state ([#4662](https://github.com/getsentry/sentry-dotnet/pull/4662))
 - The SDK now makes use of the new SessionEndStatus `Unhandled` when capturing an unhandled but non-terminal exception, i.e. through the UnobservedTaskExceptionIntegration ([#4633](https://github.com/getsentry/sentry-dotnet/pull/4633))
+- Added a new SDK `Sentry.Extensions.AI` which allows LLM usage instrumentation via `Microsoft.Extensions.AI` ([#4657](https://github.com/getsentry/sentry-dotnet/pull/4657))
 
 ### Fixes