feature: line continuation block

[hax]

div for a in listA,
\       b in listB,
        c in listC
-
  span = a
  span = b

It also require to change the parser behavior of - and -- block.

[hax]

Alternative:

div for a in listA,
\\      b in listB,
        c in listC
\
  span = a
  span = b

div for a in listA,
\       b in listB,
\       c in listC
  span = a
  span = b

Use \ for one line continuation, and \\ for line continuation block.