feat: createLayout's justify sets lines to fill the width at their word separators after the typesetter breaks them, so a kept typesetter is justified again at another width without shaping anything

[sidorares]

justify is bits: 1 sets every line that goes on to another to fill
maxWidth, as CSS's text-align: justify does; 2 sets the paragraph's
last line and each a forced break ends; 3 sets every line. What a line
leaves of the width is shared equally among its spaces and no-break spaces
before the white space it ends on, which hangs and takes none, as CSS Text
3 has text-justify: auto for the scripts that space their words and as
ntk sets it on X11. A line with no separator, or none of the width to
spare, keeps the place align gives it, and a line an ellipsis ends is not
justified.

It is not CTLineCreateJustifiedLine. Once a line's spaces have taken some
share of their own advance, CoreText spaces the letters as well, 0.2 px a
letter on a line of Helvetica with two spaces in it, where a browser widens
the separators and nothing else; and it gives the space a line ends on no
advance at all. So the line keeps the typesetter's glyphs, and keeps its
separators' left edges and widths with the room each takes. Its runs, its
carets, its hit tests, drawLayout, drawLayoutGradient and
layoutCoverage put a glyph that many shares right of where the typesetter
set it as there are separators left of it. A justified line is drawn a run
at a time, through the path a line of a scaled face's bitmap glyphs already
took.

react-x11-components' <Html> justifies by giving every space a span of its
own and laying the paragraph out again with each spaced by its line's
share, through the kerning attribute: a new attributed string, and so a new
typesetter, at every width a resize passes. On the Zen Garden's justified
designs that was most of every frame. With justify the paragraph's kept
typesetter is broken and spaced again, and nothing is shaped.

test/text-justify.js holds the lines to the breaks they have unjustified
and to the width, each space to its share and nothing else to any, a
no-break space to a separator and a line without one to its alignment, the
bits to their lines, a right-to-left paragraph to its right edge, carets and
hit tests to the spacing, a kept typesetter and a font at 2x to the same,
and the drawing: the glyphs before a justified line's first space are the
unjustified line's pixel for pixel, and its last word ends at the width.