Fix README to allow `test` as `NODE_ENV` (#1722)
Fix README to allow `test` as `NODE_ENV` (#1722)

`NODE_ENV=test` is allowed by https://github.com/rails/webpacker/pull/1563.
rails/webpacker,rossta/webpacker,rails/webpacker,gauravtiwari/webpacker,rossta/webpacker,gauravtiwari/webpacker,gauravtiwari/webpacker,rossta/webpacker,rossta/webpacker