babel-preset-react-app: add babel-plugin-relay

Adds support for Relay Modern. relay-compiler, relay-runtime, and
react-relay are all "peer" dependencies, including the script to run
relay compiler. This at least unblocks CRA from being able to develop
Relay Modern.

https://facebook.github.io/relay/docs/babel-plugin-relay.html
https://facebook.github.io/relay/docs/relay-compiler.html

Author: maletor

packages/babel-preset-react-app/index.js

@@ -9,6 +9,8 @@
 'use strict';
 
 const plugins = [
+  // Support for Relay modern.
+  require.resolve('babel-plugin-relay'),
   // class { handleClick = () => { } }
   require.resolve('babel-plugin-transform-class-properties'),
   // The following two plugins use Object.assign directly, instead of Babel's

packages/babel-preset-react-app/package.json

@@ -12,6 +12,7 @@
   ],
   "dependencies": {
     "babel-plugin-dynamic-import-node": "1.0.2",
+    "babel-plugin-relay": "1.0.1",
     "babel-plugin-syntax-dynamic-import": "6.18.0",
     "babel-plugin-transform-class-properties": "6.24.1",
     "babel-plugin-transform-object-rest-spread": "6.23.0",