A vertical ellipsis [0] would be a single character comprising three dots, just as the horizontal ellipsis (&hellip; in HTML, looks like "..." but is a single character) does, but vertical instead of horizontal.  This has the formal semantics of a token standing for something that has been left out, so would be the semantically correct thing to use here.  However, unless there's a convenient way to specify that in markdown, your three lines each with just a dot on it will do.
[0] http://www.fileformat.info/info/unicode/char/22ee/