Adding description of 'fields' option for 'validate' (#7598)

lib/instance.js

@@ -798,6 +798,7 @@ Instance.prototype.reload = function(options) {
  *
  *
  * @param {Object} [options] Options that are passed to the validator
  * @param {Object} [options] Options that are passed to the validator
  * @param {Array} [options.skip] An array of strings. All properties that are in this array will not be validated
  * @param {Array} [options.skip] An array of strings. All properties that are in this array will not be validated
+ * @param {Array} [options.fields] An array of strings. Only the properties that are in this array will be validated.
  * @see {InstanceValidator}
  * @see {InstanceValidator}
  *
  *
  * @return {Promise<undefined|Errors.ValidationError>}
  * @return {Promise<undefined|Errors.ValidationError>}