Optimize chapter end time handling in artplayer-plugin-chapter

docs/assets/example/chapter.js

@@ -21,7 +21,7 @@ var art = new Artplayer({
                 { start: 18, end: 36, title: '谁でもいいはずなのに' },
                 { start: 36, end: 54, title: '夏の想い出がまわる' },
                 { start: 54, end: 72, title: 'こんなとこにあるはずもないのに' },
-                { start: 72, end: 90, title: '终わり' },
+                { start: 72, end: Infinity, title: '终わり' },
             ]
         }),
     ],