https://en.wikipedia.org/wiki/Markdown

There is no official Markdown specification and there are many different \
implementations.\
This seems intended by the creators of the language.

#### TODO

- count number of headings for each heading level
(loop through all headings, find the highest heading level, get all used levels\
then create a slice or slice of maps and append after each deeper level discovered...)
- add docs
- delph deeper into different Markdown implementations (like CommonMark)
- add support for "Setext-style headers"