Consider support for Quarto qmd format?

I wonder whether you would also consider supporting the new Quarto qmd format.

Why?

Because Quarto is looking like a very nice system for writing books and reports with excecutable documents, such as Jupyter and R notebooks. Qmd format is Quarto’s cross-language text format for notebooks. It assumes .Rmd files are R notebooks, so Qmd format is the natural format for Jupyter notebooks in text form. We (@stefanv and I) are writing our new edition of a statistics book using Quarto. It would be a significant gain in usability if we could use the Jupytext / Notebook integration to edit and execute our documents in native Qmd format (although we are using Rmd at the moment).

What?

It’s a slightly modified version of .Rmd format, where the cell metadata goes in comments at the top of the cell, as in:

```{python}
#| warning: false
#| echo: true
...
```

[mwouts]

The new version jupytext==1.12.0 is available on pip. Thanks to everyone, especially @jjallaire and @cderv for your help here!

(As a follow-up I’ll try to install quarto on binder so that people can try it right away)

[cderv]

Ok, I’ll work on something then. This will be a simple action with probably no parameter until it will make sense to choose a specific release, instead of development version.