chore: fix lint issues

src/locale/index.ts

@@ -2,7 +2,8 @@ import { ref } from 'vue';
 import { deepAssign } from '../utils/deep-assign';
 import defaultMessages from './lang/zh-CN';
 
-type Messages = Record<string, Record<string, any>>;
+type Message = Record<string, any>;
+type Messages = Record<string, Message>;
 
 const lang = ref('zh-CN');
 const messages = ref<Messages>({
@@ -10,16 +11,16 @@ const messages = ref<Messages>({
 });
 
 export default {
-  messages() {
+  messages(): Message {
     return messages.value[lang.value];
   },
 
-  use(newLang: string, newMessages?: object) {
+  use(newLang: string, newMessages?: Message) {
     lang.value = newLang;
     this.add({ [newLang]: newMessages });
   },
 
-  add(newMessages = {}) {
+  add(newMessages: Message = {}) {
     deepAssign(messages.value, newMessages);
   },
 };