mrdocs::doc::ThematicBreakBlock

You can use an asterisk (), dash (‐), or underscore ().

There must be at least three characters in a row.

Spaces can be used between the characters, but no other characters.

The thematic break should be on its own line, separated by blank lines above and below.

Thematic breaks can also be used inside lists, but the character used for the break must be different from the list marker.