Playback rate (#411)

* update

packages/artplayer/src/player/flipMix.js

@@ -1,4 +1,4 @@
-import { errorHandle, def } from '../utils';
+import { def, capitalize } from '../utils';
 
 export default function flipMix(art) {
     const {
@@ -11,20 +11,14 @@ export default function flipMix(art) {
         get() {
             return $player.dataset.flip || 'normal';
         },
-        set(flip) {
-            if (!flip) flip = 'normal';
-
-            const flipList = ['normal', 'horizontal', 'vertical'];
-            errorHandle(flipList.includes(flip), `'flip' only accept ${flipList.toString()} as parameters`);
-
+        set(flip = 'normal') {
             if (flip === 'normal') {
                 delete $player.dataset.flip;
             } else {
                 $player.dataset.flip = flip;
             }
 
-            const word = flip.replace(flip[0], flip[0].toUpperCase());
-            notice.show = `${i18n.get('Video Flip')}: ${i18n.get(word)}`;
+            notice.show = `${i18n.get('Video Flip')}: ${i18n.get(capitalize(flip))}`;
             art.emit('flip', flip);
         },
     });