Add to changelog

Author: cderv

news/changelog-1.9.md

@@ -136,9 +136,10 @@ All changes included in 1.9:
 
 - (): New `quarto call build-ts-extension` command builds a TypeScript extension, such as an engine extension, and places the artifacts in the `_extensions` directory. See the [engine extension pre-release documentation](https://prerelease.quarto.org/docs/extensions/engine.html) for details.
 
-### `install verapdf`
+### `install`
 
 - ([#4426](https://github.com/quarto-dev/quarto-cli/issues/4426)): New `quarto install verapdf` command installs [veraPDF](https://verapdf.org/) for PDF/A and PDF/UA validation. When verapdf is available, PDFs created with the `pdf-standard` option are automatically validated for compliance. Also supports `quarto uninstall verapdf`, `quarto update verapdf`, and `quarto tools`.
+- ([#11877](https://github.com/quarto-dev/quarto-cli/issues/11877), [#10961](https://github.com/quarto-dev/quarto-cli/issues/10961), [#6821](https://github.com/quarto-dev/quarto-cli/issues/6821)): New `quarto install chrome-headless-shell` command downloads [Chrome Headless Shell](https://developer.chrome.com/blog/chrome-headless-shell) from Google's Chrome for Testing API. This is the recommended headless browser for diagram rendering (Mermaid, Graphviz) to non-HTML formats. Smaller and lighter than full Chrome, with fewer system dependencies.
 
 ### `preview`