feat: Guild Forum channel

https://github.com/discordjs/discord.js/pull/8651

src/structures/Message.js

@@ -61,6 +61,17 @@ class Message extends Base {
      */
     this.id = data.id;
 
+    if ('position' in data) {
+      /**
+       * A generally increasing integer (there may be gaps or duplicates) that represents
+       * the approximate position of the message in a thread.
+       * @type {?number}
+       */
+      this.position = data.position;
+    } else {
+      this.position ??= null;
+    }
+
     /**
      * The timestamp the message was sent at
      * @type {number}
@@ -860,7 +871,7 @@ class Message extends Base {
 
   /**
    * Create a new public thread from this message
-   * @see ThreadManager#create
+   * @see GuildTextThreadManager#create
    * @param {StartThreadOptions} [options] Options for starting a thread on this message
    * @returns {Promise<ThreadChannel>}
    */