[i18n] Add translator notes for footer letter prefixes
[i18n] Add translator notes for footer letter prefixes

Frenzie/koreader,koreader/koreader,NiLuJe/koreader,Hzj-jie/koreader,mwoz123/koreader,poire-z/koreader,poire-z/koreader,NiLuJe/koreader,Markismus/koreader,pazos/koreader,mihailim/koreader,Frenzie/koreader,koreader/koreader