fix: use translated version of appendices too

[truecluster]

Thank you Maelle! This branch works for me. I now have 3 languages with named Parts (not part files) and chapters. Is it possible to have language-specific _quarto.yml? In my case the book should have parts sorted by part names and chapter names. I.e. the part names need translation and different ordering.

[maelle]

Awesome!

you can translate part names, example: https://github.com/ropensci/dev_guide/blob/12f4c8211f76700b2f56afff5ad62592b8b72f98/_quarto.yml#L50

A different ordering however is not possible at the moment.

[truecluster]

Thank you, Maelle