Implement 'Modify Guild Channel Positions' (#1198)

* Adding shuffleArray method to utils

* Shuffle channels functionality on guild.

* Comment fix

* Removing shuffle functionality and replacing with a simple update

* Code review changes to method/variable names

* Update comment reference to channelId as well

* Updating jsdoc with typedef of ChannelPosition

src/structures/Guild.js

@@ -633,7 +633,27 @@ class Guild {
    *  .catch(console.error);
    */
   createChannel(name, type, overwrites) {
-    return this.client.rest.methods.createChannel(this, name, type, overwrites);
+    return this.client.rest.methods.updateChannel(this, name, type, overwrites);
+  }
+
+  /**
+   * The data needed for updating a channel's position.
+   * @typedef {Object} ChannelPosition
+   * @property {string} id The channel being updated's unique id.
+   * @property {number} position The new position of the channel.
+   */
+
+  /**
+   * Updates this guild's channel positions as a batch.
+   * @param {Array<ChannelPosition>} channelPositions Array of objects that defines which channel is going where.
+   * @returns {Promise<Guild>}
+   * @example
+   * guild.updateChannels([{ id: channelID, position: newChannelIndex }])
+   *  .then(guild => console.log(`Updated channels for ${guild.id}`))
+   *  .catch(console.error);
+   */
+  updateChannelPositions(channelPositions) {
+    return this.client.rest.methods.updateChannelPositions(this.id, channelPositions);
   }
 
   /**