I have a react-rails application. In some of my react views I import some styles as suggested in the package documentation, for example;

import "react-dates/lib/css/_datepicker.css";

or

import "react-image-lightbox/style.css";

In my local development environment the styles are imported all right, but when I deploy the app to Heroku on a production environment the styles stop showing and I am forced to copy-paste them from the package repo and add them on a CSS stylesheet directly on my app.

How could I have these imports working even when deployed on Heroku?