Test forming and breaking ligatures.
Allow breaking at character bounds.
Use a single list of line breaking alternatives.
Clarify meaning of Array in Paragraph.
Implement trimming spaces at end of lines.
Remove redundant overflow handling.
This may be useful later when words are allowed to overflow, but this
code path is currently unused.
Decompose ProtoFragment construction.
Add dropWhileEnd to SeparableTextContainer.
Add trivial instances of text containers.
Ensure paragraph rect is unaffected by spans.
Fix documentation of ProtoFragment after RTL placement.
Insert extra test to work around segmentation fault.
Without the added test, the test suite causes a segmentation fault
after starting "wraps by characters when line is ultra narrow".
Add line wrapping tests with spans.
Implement correct positioning of RTL runs.
Make SpanOptions a separate type.
Slightly decompose the Plain module.
Update documentation and derived instances.
Expose ParagraphConstruction.