Depending on the browser in different situations the root node itself is
selected and new text ends up in a text node on root level instead of a new
paragraph. This happens in:
* Firefox: after inserting a closed block like a horizontal rule
* Chromium: after inserting or selecting such a closed block
Now instead of inserting a paragraph directly after inserting an HR, the editor
simply checks for normal text input inside the root node and wraps the newly
written text with a paragraph (and moves the caret to the end of the paragraph
because chromium moves it to the beginning of the line)
this loops the search for marks until a block element is found, because marks
are nested elements like for example `<p><b><i>bold and italic</i></b></p>`.
this includes standard block elements (headers, paragraphs, lists, rulers)
but not marks (bold, italic)
and for sure not special elements like the stat block
