[release checklist] update changelog

Author: gordonwoodhull

news/changelog-1.7.md

@@ -2,6 +2,8 @@
 
 ## In this release
 
+## In previous releases
+
 - ([#6607](https://github.com/quarto-dev/quarto-cli/issues/6607)): Add missing beamer template update for beamer theme options: `colorthemeoptions`, `fontthemeoptions`, `innerthemeoptions` and `outerthemeoptions`.
 - ([#12625](https://github.com/quarto-dev/quarto-cli/pull/12625)): Fire resize event on window when light/dark toggle is clicked, to tell widgets to resize.
 - ([#12657](https://github.com/quarto-dev/quarto-cli/pull/12657)): Load Giscus in generated script tag, to avoid wrong-theming in Chrome.