row/col outline level (grouping) support

[mtannaan]

Hi. Thank you for providing this wonderful library, which is so simple to use! (I also use Python's openpyxl, but tired of its messy API...)

I personally had a work where I had to group rows/columns, just like the following article:
https://oxen.tech/blog/grouping-excel/

I forked xlixlsx and made some changes to do this.
I'd appreciate it if you review and merge my changes so that everyone can use this feature via Hex!

Your comments and edits are very appreciated.

[xou]

Hi!

Thanks for adding this feature!
"Outline Levels" is unfortunately not trivial to understand without knowledge of how this is implemented (or the xlsx spec). I am wondering whether a better interface could take parameters such as (group_rows: [[1, 10], [3, 5, hide:true]]); and the outline levels (and "hidden" parameter) are then calculated automatically?

WDYT?

[mtannaan]

Thanks for the response!
Sounds great, we are "grouping rows" when using Excel, rather than "setting outline levels."
I'll make some edits to support this.

[mtannaan]

Changed row/col_outline_levels to group_rows/columns and added support for :collapsed option.
I'd be glad if you check this is aligned to your suggestion.

[xou]

Awesome, thanks for this!