fix typedef

Author: danivek

lib/JSONAPISerializer.js

@@ -1000,6 +1000,7 @@ module.exports = class JSONAPISerializer {
  * @property {string|Function} type a string or a function for the type to use for serializing the relationship (type need to be register)
  * @property {string} [alternativeKey] an alternative key (string or path) to use if relationship key not exist (example: 'author_id' as an alternative key for 'author' relationship)
  * @property {string} [schema] a custom schema for serializing the relationship. If no schema define, it use the default one.
+ * @property {Function} [data] a function which returns the data to serialize for the relationship
  * @property {Function|object} [links] describes the links for the relationship
  * @property {Function|object} [meta] describes meta that contains non-standard meta-information about the relationship
  * @property {Function} [deserialize] describes the function which should be used to deserialize a related property which is not included in the JSON:API document