Add line wrapping tests with spans.

Make SpanOptions a separate type.

Hide Rect union from public interface.

The function behaves in a specific way that should not be relied on by
other modules.

Move non-public modules into Internal namespace.

Make ParagraphConstruction more efficient.

Make paragraphRect origin always 0,0.

This convention should make it easier for the caller to properly place
the paragraph within a document.

Add test for RTL text.

Remove obsolete TODO.

Test line splitting with many runs.

Add ignored prefixes and suffixes to test data.

This ensures that implementation does not rely on the texts having zero
offset inside their byte arrays.

Remove I8/Int distinction.

The distinction was meant to provide additional type safety, but
inconsistency with other used libraries required too many workarounds
for this to be beneficial.

Minimise working with Data.Text.Internal.

Use ICU to find line break boundaries.

Implement line breaking on code point boundaries.

Implement run splitting.

Store span index in ResolvedSpan.

Link to Span using a generic wrapper.

Implement absolute line heights with half-leadings.

Use CSS-compatible line height settings.

Fix pretty printing for fragmented spans.