v0.3.0

Added

• mask takes an object naming, per level, how far the clip reaches past the box across
  the line: mask: { lines: ".25em" }. Display type set tighter than its glyph boxes
  leaves descenders and accents outside the line box, and a clip at the box cuts them
  until it is dropped; a reach keeps them in the window with no change to layout, since it
  is a negative inset on the clip itself. Read the clip back off the mask's inline style
  to restore it after clearing it.