localStorage 添加 del 方法

packages/artplayer/src/storage.js

@@ -25,6 +25,12 @@ export default class Storage {
         window.localStorage.setItem(this.name, JSON.stringify(storage));
     }
 
+    del(key) {
+        const storage = this.get();
+        delete storage[key];
+        window.localStorage.setItem(this.name, JSON.stringify(storage));
+    }
+
     clean() {
         window.localStorage.removeItem(this.name);
     }