~jaro/balkon

ref: 81d758baf4c7f7ab803edccb4dd1bb7e82a4753d balkon/src d---------
Fix documentation: incorrect reference.
Fix documentation: references to non-imported names.
Fix documentation: references to local names.
Separate internal plain Paragraph/ParagraphLayout.
Expose text slicing functions.
Decompose text slicing.
Integrate BiDi reordering.
Implement BiDi resolved level reordering.
Represent lines with non-empty lists.

We can do this because we removed lines with zero size.
Remove lines with zero size.

These lines would otherwise affect line numbering.
Do not re-export through the Plain module.
Move paragraphSpanBounds to the correct module.
Clarify comment about BiDi.
Correct comment about fragmentation.
Fix style: long lines.
Fix style: small Prelude imports.
Fix style: external vs internal imports.
Fix style: white space in lambdas.
Fix style: white space around operators.
Fix style: white space in exports and imports.
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