[doc] WidgetContainer: fix some typos
[doc] WidgetContainer: fix some typos
Hzj-jie/koreader,houqp/koreader,poire-z/koreader,poire-z/koreader,NiLuJe/koreader,Markismus/koreader,koreader/koreader,NiLuJe/koreader,Frenzie/koreader,mihailim/koreader,Frenzie/koreader,koreader/koreader,lgeek/koreader,pazos/koreader,apletnev/koreader,mwoz123/koreader