Deduplicate pagination code.

Implement Rich pagination.

Qualify Plain pagination.

Make paginateAll generic.

Add user data to spans.

Fix documentation: missing Paginable.

Fix documentation: document remaining names.

Separate internal plain Paragraph/ParagraphLayout.

Fix style: white space in exports and imports.

Fix style: bullet points in comments.

Improve documentation for pagination.

Prepare pagination for future layout types.

Add paragraph pagination.