Update SyncPlay references to use plugin

src/plugins/syncPlay/plugin.ts

@@ -12,6 +12,7 @@ class SyncPlayPlugin implements Plugin {
     id: string;
     type: string;
     priority: number;
+    instance: typeof SyncPlay;
 
     constructor() {
         this.name = 'SyncPlay Plugin';
@@ -21,6 +22,8 @@ class SyncPlayPlugin implements Plugin {
         this.type = PluginType.SyncPlay;
         this.priority = 1;
 
+        this.instance = SyncPlay;
+
         this.init();
     }