* Polish zh-cn js translation

* fixes for problems pointed out by gumblex in #2044
* more effectively differentiate between following/follower

* Fix missing period (zh-cn js)

Maybe squash this commit?

* Fix duplicate word (zh-cn js)

This single-file commit, heavily based on the zh-hk version as of
ec9999c, fixes the missing js locale. Intentional, significant
departures from current zh-cn yml localizations have been marked with
rationales given.