docs: Follow-up editorial for GraphQL Playground doc. (#1270).

docs/_config.yml

@@ -21,7 +21,7 @@ sidebar_categories:
     - features/data-sources
     - features/subscriptions
     - features/metrics
-    - features/playground
+    - features/graphql-playground
     - features/scalars-enums
     - features/unions-interfaces
     - features/directives

docs/source/features/graphql-playground.md

@@ -0,0 +1,48 @@
+---
+title: GraphQL Playground
+description: Visually exploring an Apollo Server
+---
+
+[GraphQL Playground](https://github.com/prismagraphql/graphql-playground) is a graphical, interactive, in-browser GraphQL IDE, created by [Prisma](https://www.prisma.io/) and based on [GraphiQL](https://github.com/graphql/graphiql).
+
+In development, Apollo Server enables GraphQL Playground on the same URL as the GraphQL server itself (e.g. `http://localhost:4000/graphql`) and automatically serves the GUI to web browsers.  When `NODE_ENV` is set to `production`, GraphQL Playground (as well as introspection) is disabled as a production best-practice.
+
+<div align="center">
+![GraphQL Playground](../images/graphql-playground.png)
+</div>
+
+## Enabling GraphQL Playground in production
+
+To enable GraphQL Playground in production, an integration package must be installed to provide more control over the middlewares used. The following example uses the express integration:
+
+```bash
+npm install --save apollo-server-express@rc graphql
+```
+
+Introspection and the GUI can be enabled explicitly in the following manner.
+
+```js line=8,16
+const { ApolloServer } = require('apollo-server-express');
+const express = require('express');
+const { typeDefs, resolvers } = require('./schema');
+
+const server = new ApolloServer({
+  typeDefs,
+  resolvers,
+  introspection: true,
+});
+
+const app = express();
+
+// `gui` accepts a GraphQL Playground configuration
+server.applyMiddleware({
+  app,
+  gui: true,
+});
+
+app.listen({ port: 4000 }, () =>
+  console.log(`🚀 Server ready at http://localhost:4000${server.graphqlPath}`),
+);
+```
+
+> Note: When using the `apollo-server-express` package, the `apollo-server` package can be uninstalled.