TLDR: Use the create-react-app-buildpack:
$ heroku buildpacks:set mars/create-react-app
$ heroku create MY-APP --buildpack mars/create-react-app $ git add . $ git commit -m "create-react-app" $
heroku git:remote --app MY-APP$ git push heroku master
$ heroku git:remote --app MY-APP$ heroku buildpacks:set mars/create-react-app$ git commit --allow-empty -m 'Use create-react-app-buildpack'$ git push heroku master
More info: Buildpack Repo, Heroku Blog