~jaro/balkon

ref: b9ae7b26b1d948d56d3067ca828ea3d117881a7d 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.