[Sync to prerelease] Add fragoff extension to revealjs listings (#1945)

* Add fragoff extension to revealjs listings

backport of aef5413

---------

Co-authored-by: Dan Chaltiel <dan.chaltiel@gmail.com>
Co-authored-by: Christophe Dervieux <christophe.dervieux@gmail.com>

Author: 3 people

docs/extensions/listings/revealjs.yml

@@ -90,6 +90,12 @@
   description: >
     Adds flashcards in slides that you can flip and shuffle.
 
+- name: fragoff
+  path: https://github.com/DanChaltiel/quarto_fragoff
+  author: '[Dan Chaltiel](https://github.com/DanChaltiel)'
+  description: >
+    Adds a checkbox in the side panel to turn fragments on or off at runtime.
+
 - name: i18n
   path: https://github.com/ArthurData/quarto-i18n
   author: '[ArthurData](https://github.com/ArthurData)'