Frontmatter option to add numbers to headers (not anchors)

[mashehu]

From https://github.com/nf-core/website/pull/2419#pullrequestreview-1978984511

a front matter option in markdown, e.g. addHeadingNumbers: true to add numbers to the heading (there should be a remark/rehype plugin out there, but can't find one at the moment). Additionally, it should overwrite other heading numbers if present.