docs(WebhookClient): Document working options (#8375)

packages/discord.js/src/client/WebhookClient.js

@@ -29,9 +29,16 @@ class WebhookClient extends BaseClient {
    * @typedef {WebhookClientDataIdWithToken|WebhookClientDataURL} WebhookClientData
    */
 
+  /**
+   * Options for a webhook client.
+   * @typedef {Object} WebhookClientOptions
+   * @property {MessageMentionOptions} [allowedMentions] Default value for {@link WebhookMessageOptions#allowedMentions}
+   * @property {RESTOptions} [rest] Options for the REST manager
+   */
+
   /**
    * @param {WebhookClientData} data The data of the webhook
-   * @param {ClientOptions} [options] Options for the client
+   * @param {WebhookClientOptions} [options] Options for the webhook client
    */
   constructor(data, options) {
     super(options);
@@ -51,6 +58,12 @@ class WebhookClient extends BaseClient {
     Object.defineProperty(this, 'token', { value: token, writable: true, configurable: true });
   }
 
+  /**
+   * The options the webhook client was instantiated with.
+   * @type {WebhookClientOptions}
+   * @name WebhookClient#options
+   */
+
   // These are here only for documentation purposes - they are implemented by Webhook
   /* eslint-disable no-empty-function, valid-jsdoc */
   /**