~jaro/balkon

ref: b36dcd9859e8d5209a08186555b8f799ad2c8b0f balkon/src/Data/Text/ParagraphLayout/Internal/Rich d---------
Expose piecewise paragraph construction.
Consolidate tree types into one.
Add ancestor boxes to interface.
Implement Rich pagination.
Implement piecewise paragraph construction.
Add basic support for Rich layout.