~jaro/balkon

ref: 900072d27e8068ea634d9305b1370a41da9f16da 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.