[styles] Table styles read/write

[JanMarvin]

• fix reading and writing xr9 styles from R
• fix styles c++ read/write

[codecov-commenter]

Codecov Report

Merging #194 (23660f8) into main (799bae0) will increase coverage by 1.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #194      +/-   ##
==========================================
+ Coverage   81.70%   82.76%   +1.05%     
==========================================
  Files          35       35              
  Lines        7385     7386       +1     
==========================================
+ Hits         6034     6113      +79     
+ Misses       1351     1273      -78     

Impacted Files	Coverage Δ
R/class-workbook.R	75.63% <100.00%> (ø)
R/conditional_formatting.R	72.08% <100.00%> (ø)
src/styles_xml.cpp	93.27% <100.00%> (+13.84%)	⬆️

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