fix: use custom localStorage key for volume setting

src/js/plyr.js

@@ -1045,7 +1045,7 @@
 
             // Store the volume in storage
             if(config.storage.enabled && _storage().supported) {
-                window.localStorage.plyr_volume = volume;
+                window.localStorage.setItem(config.storage.key, volume);
             }
         }
 
@@ -1531,4 +1531,4 @@
         return players;
     }
 
-}(this.plyr = this.plyr || {}));
+}(this.plyr = this.plyr || {}));