Add DBNL footnotes styletweak (#7467)
Add DBNL footnotes styletweak (#7467)

`.voetnoten` is standard in DBNL ebooks.

A good test book can be found at <https://www.dbnl.org/tekst/veld028jnot01_01/>.
poire-z/koreader,koreader/koreader,Frenzie/koreader,Frenzie/koreader,NiLuJe/koreader,koreader/koreader,NiLuJe/koreader,mwoz123/koreader,poire-z/koreader