~jaro/balkon

ref: efcef179a0e0ca9bf126b3b5a32a8094f55faaf5 balkon/lib/Data d---------
Update documentation and derived instances.
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.