woql.js: add example for opt

Author: rrooij

lib/woql.js

@@ -25,6 +25,8 @@ WOQL.when = function(Query, Update){ return new WOQLQuery().when(Query, Update);
 /**
  * The Query in the Optional argument is specified as optional
  * @param {object} query - WOQL Query object
+ * @example
+ * WOQL.opt(WOQL.triple("v:optionalSubject", "v:optionalObject", "v:optionalValue"))
  * @return {object} WOQLQuery
  */
 WOQL.opt = function(query){ return new WOQLQuery().opt(query); }