~jaro/balkon

ref: 7dc45d1deab5d7d7e967fe2056f322f0dabac0bc balkon/src/Data/Text/ParagraphLayout/Internal/Plain d---------
Use more specific name for the LineHeight typeclass.
Prevent empty shaped runs.

This is in preparation for a breaking change that introduces some
empty fragments into the output. Since the shaped runs output is not
concerned with runs of zero glyphs, these will be proactively removed.
Refactor lineNumbers into a common module.
Refactor pagination to allow rich layout.
Separate interface-independent constants.
Add user data to spans.
Separate internal plain Paragraph/ParagraphLayout.