docs(association): options.through.where support

lib/associations/belongs-to-many.js

@@ -411,6 +411,7 @@ class BelongsToMany extends Association {
    * @param {object} [options.where] An optional where clause to limit the associated models
    * @param {object} [options.where] An optional where clause to limit the associated models
    * @param {string|boolean} [options.scope] Apply a scope on the related model, or remove its default scope by passing false
    * @param {string|boolean} [options.scope] Apply a scope on the related model, or remove its default scope by passing false
    * @param {string} [options.schema] Apply a schema on the related model
    * @param {string} [options.schema] Apply a schema on the related model
+   * @param {object} [options.through.where] An optional where clause applied to through model (join table)
    *
    *
    * @returns {Promise<Array<Model>>}
    * @returns {Promise<Array<Model>>}
    */
    */