Preprocessor for numbered section headings

[StefanSalewski]

Problem

Section headings are not numbered automatically.

Manually numbering makes reordering chapters a bit difficult.

Proposed Solution

Use a mdbook preprocessor.

So I modified the provided example mdbook-remove-emphasis, resulting in https://github.com/StefanSalewski/mdbook-section-numbers

For me it seems to work, and it might help others who prefer numbered section headings as well.

Notes

I do not yet understand all the details of the provided example. This tools is more a tiny Rust exercise. Actually I do not assume that many people might be interested in this tool, as not that much people are writing mdbook online books and desire numbered sections. So, if you try this preprocessor, be carefully, make a backup of your book. You might have to adapt the program code or the Cargo.toml file. Actually I can not imagine that this tool can damage your books, as it does not modify the book's sources, but only the HTML output.