NewsDownloader: add support for RDF feeds (#8822)
NewsDownloader: add support for RDF feeds (#8822)

Fixes #8799.
poire-z/koreader,Frenzie/koreader,NiLuJe/koreader,poire-z/koreader,koreader/koreader,NiLuJe/koreader,koreader/koreader,Frenzie/koreader