docs update

packages/artplayer/src/mask.js

@@ -8,7 +8,8 @@ export default class Mask {
             option,
             refs: { $mask },
         } = art;
-        append($mask, option.icons.playBig || icons.playBig);
+        const $playBig = append($mask, '<div class="art-playBig"></div>');
+        append($playBig, option.icons.playBig || icons.playBig);
     }
 
     show() {

packages/artplayer/src/style/mask.scss

@@ -11,7 +11,7 @@
         height: 100%;
         pointer-events: none;
     
-        .art-icon-playBig {
+        .art-playBig {
             position: absolute;
             right: 30px;
             bottom: 65px;