Update docs changelog (for PR #56907) (#57083)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: hubwriter <[email protected]>

Author: 3 people

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Docs changelog
 
+**12 August 2025**
+
+We have added a tutorial for using Copilot to create Mermaid diagrams at [Creating Diagrams](https://docs.github.com/en/copilot/tutorials/copilot-chat-cookbook/communicate-effectively/creating-diagrams).
+
+<hr>
+
 **4 August 2025**
 
 To address common pain points that developers face when remediating a leaked secret, we created a new article, "[Remediating a leaked secret](https://docs.github.com/en/code-security/secret-scanning/working-with-secret-scanning-and-push-protection/remediating-a-leaked-secret)".