(Automatically) Numbered Headings

[michaelweinold]

As mentioned by @rchiodo in #1348 (comment), automatically numbering markdown headings would need to be a separate feature request from the outline view, which was implemented with #1348.

Expected behaviour: Option to automatically number markdown headings, such that for:

we would get:

Existing implementation in JupyterLab: toc2 extension
Existing implementation for pure markdown files: Markdown All in One: Add/Update section numbers

[jcsaaver]

Still hoping for this to be implemented