add themeMix

packages/artplayer/src/player/themeMix.js

@@ -0,0 +1,18 @@
+import { def } from '../utils';
+
+export default function themeMix(art) {
+    const {
+        option,
+        template: { $player },
+    } = art;
+
+    def(art, 'theme', {
+        get() {
+            return $player.style.getProperty('--theme');
+        },
+        set(theme) {
+            option.theme = theme;
+            $player.style.setProperty('--theme', theme);
+        },
+    });
+}