Down-level headings in markdown files

Currently when headings are rendered in markdown files, they are rendered as-is (i.e. an h1 in a markdown file gets rendered as an h1 in the styleguide). However, the sections titles also use headings, so you can get strange behaviour such as an h1 being rendered inside a section with an h3 title, when it should be an h4.

A solution to this is to just start the headings in the markdown files at the appropriate size, but this gets tedious to update when moving sections around (i.e. moving a top-level section to a sub-section).

It would be nice if the headings in the markdown were automatically "down-levelled", I.e. h1 elements inside a markdown file inside a section with an h3 heading were converted to h4 elements.