Add slider to scroll through screenshots gallery

Thanks for the link! We need to focus on the mobile experience first, and the desktop one second. Your current demo is not ready for our case yet. Can we check how it's done on some other cool websites and do it in a similar (maybe simpler) way?

1. On mobile, one screenshot should take almost all the screen, and auto-scroll or scroll by tap.
2. For iOS users iOS screenshots are needed, for Android - Android ones (we can do it later, but keep it in mind now).
3. Screenshots may be localized, e.g. French-speaking users may see France on screenshots.
4. On Desktops and tablets, maybe also on mobiles in a landscape, there's plenty of space to show several screenshots depending on the available width.

Originally posted by @biodranik in https://github.com/organicmaps/organicmaps.github.io/pull/145#issuecomment-1732961253