add app icon

src/modules/portal/views/home/Home.vue

@@ -8,6 +8,10 @@
             style="display: inline-block; font-size: 20px; line-height: 48px; width: 100%; text-decoration-line: none"
             title="回到主页"
           >
+            <img
+              src="./icon.png"
+              style="width: 20px; height: 20px; line-height: 48px; display: inline-block"
+            />
             云平台主页
           </router-link>
         </el-menu-item>