~jaro/balkon

ref: 4c1db0da368a4d8a2a33ab0d37deef45e99a54d2 balkon/lib/Data/Text 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.