Hyphenation: add custom hyphenation rules (#7746)

The hyphenation of a word can be changed from its default
by long pressing for 3 seconds and selecting 'Hyphenate'.
These overrides are stored in a per-language file, i.e:
koreader/settings/user-German.hyph.

frontend/ui/widget/trapwidget.lua

@@ -155,6 +155,7 @@ function TrapWidget:onCloseWidget()
             return "ui", self.frame.dimen
         end)
     end
+    return true
 end
 
 return TrapWidget