~jaro/balkon

ref: 2db7d32290bc20ee29469a9edf0d64d3dbad93c9 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.