feat: add Chinese-English language toggle

mail-vue/src/i18n/en.js

@@ -312,9 +312,9 @@ const en = {
     character: '',
     mustNotContain: 'Must Not Contain',
     mustNotContainDesc: 'Separate with commas',
-    blackSubjectDesc: '输入多个值用,分开',
-    blackContentDesc: '输入多个值用,分开',
-    blackFromDesc: '输入多个值用,分开',
+    blackSubjectDesc: 'Subject',
+    blackContentDesc: 'Content',
+    blackFromDesc: 'Sender or domain',
     setSuccess: 'Settings saved successfully',
     details: 'Details',
     userDetails: 'User Details',

mail-vue/src/i18n/zh.js

@@ -246,7 +246,7 @@ const zh = {
     serverBusyErrorMsg: '服务器繁忙，请稍后重试',
     reqFailErrorMsg: '请求失败，请稍后再试',
     message: '邮件详情',
-    language: '网站语言',
+    language: '系统语言',
     totalUserAccount: '{msg} 个',
     sendBanned: '已禁用',
     sendInternal: '仅站内',