Fix dev server config

Author: Morten N.O. Henriksen

packages/react-scripts/config/webpackDevServer.config.js

@@ -84,11 +84,13 @@ module.exports = function (proxy, allowedHost) {
       path: sockPath,
       port: sockPort,
     },
-    // It is important to tell WebpackDevServer to use the same "publicPath" path as
-    // we specified in the webpack config. When homepage is '.', default to serving
-    // from the root.
-    // remove last slash so user can land on `/test` instead of `/test/`
-    publicPath: paths.publicUrlOrPath.slice(0, -1),
+    dev: {
+      // It is important to tell WebpackDevServer to use the same "publicPath" path as
+      // we specified in the webpack config. When homepage is '.', default to serving
+      // from the root.
+      // remove last slash so user can land on `/test` instead of `/test/`
+      publicPath: paths.publicUrlOrPath.slice(0, -1),
+    },
 
     https: getHttpsConfig(),
     host,