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

• print header tree
• delph deeper into different Markdown implementations (like CommonMark)
• add support for "Setext-style headers"

logic ideas

For a tree structure you will probably need parent/child relationships.
You might need to create a parent and a child field in the header struct.