fix [webpack-cli] Invalid options object (firewall renamed to allowedHosts)

[oguennec]

This PR is meant to fix the following error while running navbar locally.

➜  navbar git:(master) ✗ yarn start:standalone
yarn run v1.22.19
$ webpack serve --env standalone
[webpack-cli] Invalid options object. Dev Server has been initialized using an options object that does not match the API schema.
 - options has an unknown property 'firewall'. These properties are valid:
   object { allowedHosts?, bonjour?, client?, compress?, devMiddleware?, headers?, historyApiFallback?, host?, hot?, http2?, https?, ipc?, liveReload?, magicHtml?, onAfterSetupMiddleware?, onBeforeSetupMiddleware?, onListening?, open?, port?, proxy?, server?, setupExitSignals?, setupMiddlewares?, static?, watchFiles?, webSocketServer? }
 - options.client has an unknown property 'host'. These properties are valid:
   object { logging?, overlay?, progress?, reconnect?, webSocketTransport?, webSocketURL? }
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

The firewall option has been renamed as of webpack-dev-server v4.0.0-rc.0 to allowedHosts. webpack-config-single-spa must be updated to a more recent version that includes the option renaming fix.