ref: Add external contributor to CHANGELOG.md (#13727)

This PR adds the external contributor to the CHANGELOG.md file, so that
they are credited for their contribution. See #13610

---------

Co-authored-by: lforst <8118419+lforst@users.noreply.github.com>
Co-authored-by: Abhijeet Prasad <aprasad@sentry.io>

Author: 3 people

CHANGELOG.md

@@ -10,7 +10,7 @@
 
 - "You miss 100 percent of the chances you don't take. — Wayne Gretzky" — Michael Scott
 
-Work in this release was contributed by @KyGuy2002 and @artzhookov. Thank you for your contributions!
+Work in this release was contributed by @KyGuy2002, @artzhookov, and @julianCast. Thank you for your contributions!
 
 ## 8.30.0