~jaro/balkon

ref: 6e011c818a62f3d3ae7554f67f24fc8f3abf031b balkon/lib/Data/Text/ParagraphLayout d---------
Expose ParagraphConstruction.
Hide Rect union from public interface.

The function behaves in a specific way that should not be relied on by
other modules.
Use internal library to hide non-public modules.