Update docs changelog (for PR #57416) (#57655)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Anne-Marie <102995847+am-stead@users.noreply.github.com>

Author: 3 people

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Docs changelog
 
+**23 September 2025**
+
+We've added new documentation for Spark that answers some common customer questions, helps customers troubleshoot known issues, and guides users on the best ways to prompt and provide context to Spark.
+
+See:
+- "[About GitHub Spark](https://docs.github.com/en/copilot/concepts/spark)"
+- "[Troubleshooting common issues with GitHub Spark](https://docs.github.com/en/copilot/how-tos/troubleshoot-copilot/troubleshoot-spark)"
+- "[Write effective prompts and provide useful context for Spark](https://docs.github.com/en/copilot/tutorials/spark/prompt-tips)"
+
+<hr>
+
 **17 September 2025**
 
 We added documentation for expanded features for reusing workflow configurations in GitHub Actions.