We need to know if an article is front or not

[kelson42]

This has proven to be mecessary at many occasions but at least in https://github.com/kiwix/libkiwix/issues/1026#issuecomment-1860683025

I think we could achieve this by stoping the inherited hack of not saving twices in the title and path indexes if the entries are the same. That would not imply a major format change, only a minor. We could still be able to use the hack (if no front article).

At libzim level, it would be great to have a dedicated method isFront() based on how the page title is saved

[kelson42]

@mgautierfr Would that be easy to implement?