Add browser module traces metadata release notes

release notes/v0.49.0.md

@@ -33,6 +33,7 @@ _what, why, and what this means for the user_
 
 - [#3440](https://github.com/grafana/k6/pull/3440) use built-in certificates if none are provided by the OS. Thanks to `@mem` for wokring on it!
 - [browser#1135](https://github.com/grafana/xk6-browser/pull/1135) improves the array output from `console` in the k6 logs.
+- [browser#1104](https://github.com/grafana/xk6-browser/pull/1104) adds support for browser module traces metadata. Users can define *key-value* metadata that will be included as attributes in every generated span.
 
 ## Bug fixes