feat: add backtop

src/App.vue

 <template>
+  <BackTop/>
   <NavBar/>
   <router-view/>
 </template>
 
 <script>
 import NavBar from 'components/content/NavBar'
+import BackTop from 'components/common/BackTop';
 
 export default {
   name:'#app',
-  components:{NavBar}
+  components:{NavBar, BackTop}
   
 }
 </script>

src/components/common/BackTop.vue

+<template>
+  <ElBacktop>
+    <div
+        style="{
+          height: 100%;
+          width: 100%;
+          background-color: #f2f5f6;
+          box-shadow: 0 0 6px rgba(0,0,0, .12);
+          text-align: center;
+          line-height: 40px;
+          color: #31c27c;
+        }"
+      >
+      <i class="el-icon-arrow-up"></i>
+    </div>
+  </ElBacktop>
+</template>
+
+<script>
+export default {
+  name:'BackTop'
+}
+</script>
+
+<style>
+
+</style>

src/components/common/NavMenu.vue

@@ -13,7 +13,6 @@
     @click="onClik(item.path)">
     {{item.title}}
   </el-menu-item>
-
 </el-menu>
 </template>
 
@@ -33,7 +32,6 @@
         {title: '电台', path: '/MusicLibrary/radions'},
         {title: 'MV', path: '/MusicLibrary/mv'},
         ]
-
       };
     },
     methods: {