[UX] Footer: add prefix option "Compact items" (#7127)
[UX] Footer: add prefix option "Compact items" (#7127)

For a compact layout, with removed/shortened spaces.
NiLuJe/koreader,Hzj-jie/koreader,NiLuJe/koreader,Frenzie/koreader,koreader/koreader,poire-z/koreader,Frenzie/koreader,poire-z/koreader,mwoz123/koreader,koreader/koreader,pazos/koreader