:bug: bug(extend): fix TypeError: Cannot redefine property: $i18n (#422) by @HadiChen
:bug: bug(extend): fix TypeError: Cannot redefine property: $i18n (#422) by @HadiChen

* fix TypeError: Cannot redefine property: $i18n

fix https://github.com/kazupon/vue-i18n/issues/421

* flow:$FlowFixMe with object literal

kazupon/vue-i18n,kazupon/vue-i18n,kazupon/vue-i18n,kazupon/vue-i18n