README: add new logo and links from koreader.rocks homepage (#3881)
README: add new logo and links from koreader.rocks homepage (#3881)

References #3858 #2000
lgeek/koreader,NiLuJe/koreader,Markismus/koreader,koreader/koreader,koreader/koreader,mwoz123/koreader,houqp/koreader,poire-z/koreader,mihailim/koreader,Frenzie/koreader,Frenzie/koreader,NiLuJe/koreader,pazos/koreader,Hzj-jie/koreader,poire-z/koreader