Add LiveReload (#663)

lib/core/Site.js

@@ -7,11 +7,13 @@
 
 const React = require('react');
 const fs = require('fs');
+const classNames = require('classnames');
+
 const HeaderNav = require('./nav/HeaderNav.js');
 const Head = require('./Head.js');
 const Footer = require(process.cwd() + '/core/Footer.js');
 const translation = require('../server/translation.js');
-const classNames = require('classnames');
+const constants = require('./constants');
 
 const CWD = process.cwd();
 
@@ -159,6 +161,13 @@ class Site extends React.Component {
                 }}
               />
             ))}
+          {process.env.NODE_ENV === 'development' && (
+            <script
+              src={`http://localhost:${
+                constants.LIVE_RELOAD_PORT
+              }/livereload.js`}
+            />
+          )}
         </body>
       </html>
     );

lib/core/constants.js

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+module.exports = {
+  LIVE_RELOAD_PORT: 35729,
+};