- cell.r holds the raw rich text, cell.h now holds the html
(version 0.5.0 cell.raw -> cell.r, cell.r -> cell.h)
- similar changes to comments and XLSB generation
- removed some unused binary methods
Cell object stores the formatted text in the `.w` field
- Raw format and types are preserved in the `.t`, `.v` fields
- Accessors have been updated to use the field
updates for older OOXML:
- ECMA-376 makes reference to old sstItem shared string item
- [MS-XLSX] xmlns for workbook
