From the pandoc release announcement: https://github.com/jgm/pandoc/releases/3.9 :
> Starting with this release, pandoc can be compiled to WASM, making it possible to use pandoc in the browser. A full-featured GUI interface is provided at https://pandoc.org/app
Pandoc in WASM probably makes it possible to add jupytext pandoc markdown support to jupyterlite?