Add source map loader to frontend

frontend/package.json

@@ -36,6 +36,7 @@
     "webpack": "^4.43.0",
     "webpack-bundle-analyzer": "^3.9.0",
     "webpack-cli": "^3.3.11",
+    "source-map-loader": "^1.1.0",
     "webpack-dev-server": "^3.10.3"
   },
   "postcss": {

frontend/webpack.config.js

@@ -112,6 +112,11 @@ module.exports = (env, argv) => ({
         },
         exclude: /node_modules/,
       },
+      {
+        test: /\.js$/,
+        enforce: 'pre',
+        use: ['source-map-loader'],
+      },
     ],
   },
   resolve: {