add zh-cn support

src/i18n.ts

@@ -1,7 +1,7 @@
 import en from './i18n/en';
 import { createI18n } from 'vue-i18n';
 
-export type Locale = 'en' | 'ja' | 'pl';
+export type Locale = 'en' | 'ja' | 'pl' | 'zh';
 
 const loadLocaleMessages = async (locale: Locale) => {
     return (await import(`./i18n/${locale}.ts`)).default;
@@ -13,7 +13,7 @@ const i18n = createI18n({
     fallbackLocale: 'en',
     warnHtmlInMessage: false,
     warnHtmlMessage: false,
-    messages: { en, ja: {}, pl: {} },
+    messages: { en, ja: {}, pl: {}, zh: {} },
 });
 
 const setLocale = async (locale: Locale) => {