This is related to {T255224}.
Wikisource Export uses an on-wiki page ([[https://it.wikisource.org/wiki/MediaWiki:Wsexport_i18n.ini | e.g. on Italian Wikisource]]) to store the few bits of text that it includes in exported ebooks. This page is a the [[https://en.wikipedia.org/wiki/INI_file | INI format]], although its content type is wikitext.
We should change it to be a JSON page, so editors can benefit from not being allowed to save invalid syntax. Alternatively, we could look at moving these into the application and having them translated on TranslateWiki (the advantage of having them on-wiki is that then all the content that ends up in the ebook comes from the same wiki and so can be worked on by the same community).
The format looks like this:
```lang=ini
title_page = "Title page"
cover = "Cover"
exported_from_wikisource_the = "Exported from Wikisource on %d"
about = "About"
```