Support parsing of definition lists

[SamyPesse]

We should maybe support a syntax for definition lists (already supported by Kramdown and Pandoc):

kramdown
: A Markdown-superset converter

But:

• ❌ GitHub doesn't support it.
• ❌ Hard to implement in the editor
• ❌ It's possible to use HTML in markdown

[Phlow]

Just to add some information why definition lists are a fine way to structure content.

Useful for example for a list of books you add to your literture section. Or if you list interesting sources or websites at the end of an article. Or when writing an article, you could use a definition list to explain the different terms. It's also more SEO-friendly than to do it with a list.