Make all react app vars accessible in index.html (#1440)

* Make all vars accessiable in index.html

* Fix wrong env provieded to DefinePlugin

* Separate results from getClientEnvironment

* The `string` should be object instead of string

* Fix accessing wrong field

* Changed variables naming to `raw` and `stringified`

* Remove trailing commas

packages/react-scripts/config/webpack.config.dev.js

@@ -198,12 +198,11 @@ module.exports = {
     ];
   },
   plugins: [
-    // Makes the public URL available as %PUBLIC_URL% in index.html, e.g.:
+    // Makes some environment variables available in index.html.
+    // The public URL is available as %PUBLIC_URL% in index.html, e.g.:
     // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
     // In development, this will be an empty string.
-    new InterpolateHtmlPlugin({
-      PUBLIC_URL: publicUrl
-    }),
+    new InterpolateHtmlPlugin(env.raw),
     // Generates an `index.html` file with the <script> injected.
     new HtmlWebpackPlugin({
       inject: true,
@@ -211,7 +210,7 @@ module.exports = {
     }),
     // Makes some environment variables available to the JS code, for example:
     // if (process.env.NODE_ENV === 'development') { ... }. See `./env.js`.
-    new webpack.DefinePlugin(env),
+    new webpack.DefinePlugin(env.stringified),
     // This is necessary to emit hot updates (currently CSS only):
     new webpack.HotModuleReplacementPlugin(),
     // Watcher doesn't work well if you mistype casing in a path so we use