[react-packager] Add jpe?g to asset extensions

packager/packager.js

@@ -200,6 +200,7 @@ function getAppMiddleware(options) {
     cacheVersion: '2',
     transformModulePath: require.resolve('./transformer.js'),
     assetRoots: options.assetRoots,
+    assetExts: ['png', 'jpeg', 'jpg']
   });
 }