Add link to wpgraphql plugin

Author: w3bdesign

README.md

@@ -83,7 +83,7 @@ The current release has been tested and is confirmed working with the following
 
 **I am getting a cart undefined error or other GraphQL errors?**
 
-Check that you are using the 0.6.1 version of the WooGraphQL plugin
+Check that you are using the 0.6.1 version of the [wp-graphql-woocommerce](https://github.com/wp-graphql/wp-graphql-woocommerce) plugin
 
 **The products page isn't loading?**