zh-cn&tw.json: "extended info" -> "about this site" (#3519)

* zh-cn.json: "additional info" -> "more info"

This commit changes the "extended info" (about/more) text to something that translates to "more info", as "additional info" in zh can sound like appending things to the (ugh) navbar, I guess.

Or should I just change it to "about this site" (关于本站)?

* zh-cn.json: navbar.info -> "about this site"

* zh-臺灣.json: navbar.info -> "about this site"