Add message.pinned

src/structures/Message.js

@@ -28,6 +28,11 @@ class Message {
   }
 
   setup(data) {
+    /**
+     * Whether or not this message is pinned
+     * @type {Boolean}
+     */
+    this.pinned = data.pinned;
     /**
      * The author of the message
      * @type {User}