Add shaped runs to manually test pagination.

Describe box edges with extensible type.

Test interaction between boxes and mixed script.

Test line breaking in boxes.

Handle ancestor boxes in rich layout.

Add ancestor boxes to interface.

Test layout with mixed font sizes.

Test Rich pagination.

Test Rich line wrapping.

Test Rich layout.

Add user data to spans.

Add line numbers to laid out fragments.

Update formatting in golden files.

All golden files are regenerated to use the new formatting.

This only affects whitespace (including newlines), otherwise the golden
values are perfectly equal. You can check this using the command:
`git show --word-diff-regex='[^[:space:]]'`

Rename golden files for easier tracking.

Make demo font size better match window.

Add paragraph pagination.

Test removing spaces around lines.

Allow empty lines when hard line breaking.

Support hard line breaks.

Include fontInfo in the repository.

This should make it possible to use the sample test outputs straight
from the repository, without having to build and run the tests.