Not related to the question, but I'm personally using this site (https://zeit.co/) to deloy my React sites. It's a free tool that uses the CI/CD development practice, which deploys multiple branches of your GitHub project for the purpose of testing in different environments before merging anything to master (production). Whenever you push anything to GitHub, it'll get deployed immediately.
One thing I'm not certain about this site is the degree of customization it provides. I know they have a CLI tool and you can change quite a few settings with that tool, but I don't know to what extent we can configure the environment.