htmlToPlainText(): tweak format paragraphs with indentation (#7095)
htmlToPlainText(): tweak format paragraphs with indentation (#7095)

Rework dafaf966, with a tabulation instead of multiple
&nbsp; to ensure a constant indentation when text
is justified.
koreader/koreader,Frenzie/koreader,mwoz123/koreader,Hzj-jie/koreader,poire-z/koreader,NiLuJe/koreader,Frenzie/koreader,pazos/koreader,koreader/koreader,NiLuJe/koreader,poire-z/koreader,Markismus/koreader