Fix npm start issue - requires json-loader in webpack

See rjsf-team/react-jsonschema-form#1274 (comment)

Author: adamjhamer

package.json

@@ -57,6 +57,7 @@
     "file-loader": "^0.9.0",
     "gh-pages": "^0.4.0",
     "html": "0.0.10",
+    "json-loader": "^0.5.7",
     "jsdom": "^7.2.1",
     "less": "^2.7.1",
     "less-loader": "^2.2.3",

webpack.config.dev.js

@@ -66,7 +66,11 @@ module.exports = {
       {test: /\.ttf(\?v=\d+\.\d+\.\d+)?$/, loader: "url?limit=10000&mimetype=application/octet-stream"},
       {test: /\.eot(\?v=\d+\.\d+\.\d+)?$/, loader: "file"},
       {test: /\.svg(\?v=\d+\.\d+\.\d+)?$/, loader: "url?limit=10000&mimetype=image/svg+xml"},
-      {test: /\.jpg(\?v=\d+\.\d+\.\d+)?$/, loader: "url?limit=10000&mimetype=image/jpeg"}
+      {test: /\.jpg(\?v=\d+\.\d+\.\d+)?$/, loader: "url?limit=10000&mimetype=image/jpeg"},
+      {
+        test: /\.json$/,
+        loader: 'json-loader'
+      },
     ]
   }
 };