Make the dash parameter optional. This allows the function call to
be shorter in most of the cases, which is easier to read. At the same
time it is more compatible with the setLineDash and
setLineDashPattern functions of jsPDF (1.5.3 and master 20190703).
Allow an empty function call instead of an empty array (reason see above).
dashparameter optional. This allows the function call to be shorter in most of the cases, which is easier to read. At the same time it is more compatible with the setLineDash and setLineDashPattern functions of jsPDF (1.5.3 and master 20190703).resolve #23