Introduce Desktop CSS for Kiwix-Desktop App (to reveal hidden wikipedia navboxes at bottom of articles)

[knowledge-is-power]

the wikipedia zims, when opened thru kiwix-desktop app, doesnt show navigation-boxes/templates at the bottom of articles. this is because kiwix-desktop only uses mobile css (which hides navboxes). by implementing an option to use desktop css instead of default mobile css, the hidden navboxes can revealed. further, the desktop app should have desktop css to serve its purpose.

A 'quick-fix' here would be to implement an option to force-unhide the navboxes (without needing the whole css swap to desktop-style).

These solutions were originally presented by @Jaifroid here with further discussion continued from here leading to the creation of this ticket.

cc @kelson42 @Jaifroid @juuz0

[Jaifroid]

@knowledge-is-power This was a feature I originally developed for Kiwix JS for Windows and Linux. To do a full Desktop view, it's necessary to remove the mobile CSS and inject the Desktop versions that Wikipedia provides, and as this is very specific to certain ZIM types, I don't think it would be acceptable, or considered good practice, for Kiwix Desktop to take care of this feature by itself. It would, however, be acceptable for this to be a feature of the Wikipedia ZIM archives themselves. It would be relatively easy for Wikipedia ZIMs to package the appropriate Desktop CSS and an option to swap the mobile view for the desktop view as part of an API in the ZIM. Then readers could provide a UI for such an API. Even easier would be to tweak (maybe optionally) the mobile CSS so that it stops hiding this content. Again, this is probably best done at ZIM level.