Fix typo DEBUG

docs/mobile.html

@@ -45,7 +45,7 @@
     <script src="./uncompiled/artplayer-plugin-danmuku/index.js"></script>
     <script src="./uncompiled/artplayer-plugin-ads/index.js"></script>
     <script>
-        Artplayer.DEGUG = true;
+        Artplayer.DEBUG = true;
 
         var art = new Artplayer({
             container: '.artplayer-app',