add to changelog

Author: cderv

news/changelog-1.6.md

@@ -3,6 +3,7 @@
 ## In this release
 
 - ([#11561](https://github.com/quarto-dev/quarto-cli/issues/11561)): Fix a regression with `$border-color` that impacted, callouts borders, tabset borders, and table borders of the defaults themes. `$border-color` is now correctly a mixed of `$body-color` and `$body-bg` even for the default theme.
+- ([#11943](https://github.com/quarto-dev/quarto-cli/issues/11943)): Fix callout title color on dark theme in revealjs following Revealjs update in quarto 1.6.
 
 ## In previous releases