Add a bookmarking or favourites feature

[Jaifroid]

This appears to be a popular request. We always took the view with Kiwix JS apps that any bookmark feature should use the browser's native bookmarking. However, at least in PWA context and also in Electron app context, the favourites are not exposed to the app.

It's also the case that we do not have a way to open an article automatically just from a URL. QUALIFICATION: We do not have a way to open an article automatically just from a URL if the ZIM has not first been loaded. With persistent permissions and/or NodeJS FS access, this ought not to be too difficult to implement.