Review internal branding of app

[Jaifroid]

Following a recent team meeting, branding decisions for the Kiwix JS apps were recorded in the Branding document.

This issue is about reviewing the internal branding of the apps, e.g. on splash screens or About pages. The internal branding can just be "Kiwix" where this makes sense, or "Kiwix JS" where needing to distinguish between native Kiwix apps and the JS apps. For descriptions of variants, it is acceptable to add qualifiers such as "Kiwix JS (UWP)" or "Kiwix JS (Electron)" if the variants are themselves being discussed as variants, for example on the "About" page.