简化player接口

packages/artplayer/src/player/seekMix.js

@@ -4,7 +4,7 @@ export default function seekMix(art, player) {
     const { notice } = art;
 
     Object.defineProperty(player, 'seek', {
-        value: time => {
+        set(time) {
             player.currentTime = time;
             notice.show(`${secondToTime(time)} / ${secondToTime(player.duration)}`);
             art.emit('seek', time);