Improve flow of documentation around GraphiQL (#1956)

Author: benjie

Diff for: src/pages/graphql-js/running-an-express-graphql-server.mdx

@@ -52,6 +52,8 @@ You can run this GraphQL server with:
 node server.js
 ```
 
+At this point you will have a running GraphQL API; but you can't just visit it in your web browser to use it - you need a GraphQL client to issue GraphQL queries to the API. Let's take a look at how to add the GraphiQL (GraphQL with an `i` in the middle) integrated development environment to your server.
+
 ## Using GraphiQL
 
 [GraphiQL](https://github.com/graphql/graphiql) is GraphQL's IDE; a great way of querying and exploring your GraphQL API.