feat(GuildChannel): add fetchInvites method (#2339)

* feat(GuildChannel): add fetchInvites method

* fix: actually use the 'channels' endpoint

src/structures/GuildChannel.js

@@ -430,6 +430,21 @@ class GuildChannel extends Channel {
       .then(invite => new Invite(this.client, invite));
   }
 
+  /**
+   * Fetches a collection of invites to this guild channel.
+   * Resolves with a collection mapping invites by their codes.
+   * @returns {Promise<Collection<string, Invite>>}
+   */
+  async fetchInvites() {
+    const inviteItems = await this.client.api.channels(this.id).invites.get();
+    const invites = new Collection();
+    for (const inviteItem of inviteItems) {
+      const invite = new Invite(this.client, inviteItem);
+      invites.set(invite.code, invite);
+    }
+    return invites;
+  }
+
   /**
    * Clones this channel.
    * @param {Object} [options] The options