add core.js to demo

docs/mobile.html

@@ -19,7 +19,8 @@
         <div class="artplayer-app"></div>
         <p class="tip"></p>
     </div>
-    <script src="https://cdn.bootcss.com/vConsole/3.2.0/vconsole.min.js"></script>
+    <script src="./assets/js/core.js"></script>
+    <script src="./assets/js/vconsole.min.js"></script>
     <script src="./uncompiled/artplayer.js?t=6"></script>
     <script src="./uncompiled/artplayer-plugin-danmuku.js"></script>
     <script src="./assets/js/mobile.js"></script>