update readme

Author: nicosefer

README.md

@@ -18,8 +18,8 @@ JSONAPIDeserializer.deserialize(jsonapiResponse, {
 #### Available deserialize config params
 
 - **keepRelationshipsTypes**: (optional boolean default:false) Defines if relationships should keep type property.
-  If the flag is false, the value will be the relationship value will be a string | []string | null | [].
-  If the flag is true, the value will be {id, type} | []{id, type}.
+  If the flag is false, the value will be the relationship value will be a `string | []string | null | []`.
+  If the flag is true, the value will be `{id, type} | []{id, type}`.
   > Note: if the relationship has a related included object, the included object will be set as the relationship value.
 
 ### Serialization