Update README.md: more Mac info (#3787)
Update README.md: more Mac info (#3787)

References #3783.
Frenzie/koreader,NiLuJe/koreader,mihailim/koreader,poire-z/koreader,koreader/koreader,mwoz123/koreader,NiLuJe/koreader,koreader/koreader,Markismus/koreader,pazos/koreader,Frenzie/koreader,poire-z/koreader,Hzj-jie/koreader,lgeek/koreader,houqp/koreader