add maintainers of japan (vuejs#1502)

kazupon · chrisvfritz · commit 4f3a8515f487 · 2018-03-19T14:22:34.000-04:00
* add maintainers of japan

* tweak
diff --git a/README.md b/README.md
@@ -35,6 +35,9 @@ Japanese translation is maintained by [Vue.js japan user group](https://github.c
 
 * Translation Repo - [/vuejs/jp.vuejs.org](https://github.com/vuejs/jp.vuejs.org)
 * Primary maintainer - [kazupon](https://github.com/kazupon)
+* Secondary Maintainers:
+    * [re-fort](https://github.com/re-fort)
+    * [potato4d](https://github.com/potato4d)
 
 ### Korean
 
