refactor: ♻️ 演示界面统一至demo下，精简删除demo目录即可

Former-commit-id: cef5e36eb0e60299d1a72b9a12c9ea8d93a77244

src/views/demo/permission/components/SwitchRoles.vue

@@ -1,6 +1,6 @@
 <template>
   <div>
-    <div style="margin-bottom: 15px">Your roles: {{ roles }}</div>
+    <div class="mb-[15px]">Your roles: {{ roles }}</div>
     Switch roles:
     <el-radio-group v-model="switchRoles">
       <el-radio-button label="EDITOR" />

src/views/demo/table/Export2Excel.js

@@ -216,7 +216,7 @@ export function export_json_to_excel({
             wch: 10,
           };
         } else if (val.toString().charCodeAt(0) > 255) {
-        /*再判断是否为中文*/
+          /*再判断是否为中文*/
           return {
             wch: val.toString().length * 2,
           };