Convert/export notebook to other encodings like myst markdown

[crazy4pi314]

There are some great tools in the community like nbconvert that support converting notebooks to other formats like myst markdown, .rst, latex, with the help of tools like pandoc and TeX. Since notebooks themselves are becoming a popular documentation format (see things like the executable book project it would be nice to have as a part of the export menu in the notebook header that would export the notebook to say a myst markdown file.