add posterMix

packages/artplayer/src/player/posterMix.js

@@ -0,0 +1,16 @@
+import { def, setStyle } from '../utils';
+
+export default function posterMix(art, player) {
+    const {
+        option,
+        template: { $poster },
+    } = art;
+
+    def(player, 'poster', {
+        get: () => option.poster,
+        set(url) {
+            option.poster = url;
+            setStyle($poster, 'backgroundImage', `url(${url})`);
+        },
+    });
+}