Add EPUB3 extension to MuPDF document (#6013)
Add EPUB3 extension to MuPDF document (#6013)

Loads fine, see https://github.com/koreader/koreader/commit/026140f809cd8f441831bc71dc458f92b8774a62#commitcomment-38122799
NiLuJe/koreader,pazos/koreader,Frenzie/koreader,koreader/koreader,Hzj-jie/koreader,mwoz123/koreader,poire-z/koreader,Markismus/koreader,NiLuJe/koreader,poire-z/koreader,Frenzie/koreader,koreader/koreader