feat(Presence): Expose sync_id in Activity (#9766)

* feat(Presence): Expose sync_id in Activity

* chore: mention non-documentation

---------

Co-authored-by: Jiralite <33201955+Jiralite@users.noreply.github.com>

Author: almostSouji

packages/discord.js/src/structures/Presence.js

@@ -216,6 +216,13 @@ class Activity {
      */
     this.party = data.party ?? null;
 
+    /**
+     * The sync id of the activity
+     * <info>This property is not documented by Discord and represents the track id in spotify activities.</info>
+     * @type {?string}
+     */
+    this.syncId = data.sync_id ?? null;
+
     /**
      * Assets for rich presence
      * @type {?RichPresenceAssets}

packages/discord.js/typings/index.d.ts

@@ -264,6 +264,7 @@ export class Activity {
     size: [number, number];
   } | null;
   public state: string | null;
+  public syncId: string | null;
   public timestamps: {
     start: Date | null;
     end: Date | null;