ref: Add external contributor to CHANGELOG.md (#13764)

This PR adds the external contributor to the CHANGELOG.md file, so that
they are credited for their contribution. See #13673

Co-authored-by: chargome <[email protected]>

Author: github-actions[bot]

CHANGELOG.md

@@ -12,7 +12,7 @@
 - Moved description of `browser` spans into the operation, e.g. `browser - cache` -> `browser.cache` and set the URL as
   the description
 
-Work in this release was contributed by @Zen-cronic. Thank you for your contribution!
+Work in this release was contributed by @Zen-cronic and @Sjoertjuh. Thank you for your contributions!
 
 ## 8.31.0