Add reference to graphical clients as well as curl (graphql#496)

Author: nrempel

site/graphql-js/Tutorial-GraphQLClients.md

@@ -23,6 +23,8 @@ You should see the output returned as JSON:
 {"data":{"hello":"Hello world!"}}
 ```
 
+If you prefer to use a graphical user interface to send a test query, you can use clients such as [GraphiQL](https://github.com/graphql/graphiql) and [Insomnia](https://github.com/getinsomnia/insomnia).
+
 It's also simple to send GraphQL from the browser. Open up http://localhost:4000, open a developer console, and paste in:
 
 ```javascript