feat: Guild#partnered (#3444)

* feat: Guild#partnered

* typings: added Guild#features

* fix: removed trailing space

* typings: made Guild#partnered readonly

src/structures/Guild.js

@@ -403,6 +403,15 @@ class Guild extends Base {
     return new Date(this.joinedTimestamp);
   }
 
+  /**
+   * If this guild is partnered
+   * @type {boolean}
+   * @readonly
+   */
+  get partnered() {
+    return this.features.includes('PARTNERED');
+  }
+
   /**
    * If this guild is verified
    * @type {boolean}