Remove dependency on react-rails

[patrickclery]

As a developer, I'd like to be able to...

• Auth with JWT (Authenticate with Devise JWT #92)
• Use webpack without the webpacker layer
• Deploy frontend and API separately

Action Steps

• Create a separate folder using CRA
• Test that a working App component loads (before swapping in old ones)
• Migrate all old components to new CRA
• Add script to start puma + webpack-dev-server (foreman)
• Deploy on Heroku with separated concerns
• Remove react-rails and all UI/JavaScript related code

Biggest challenge will be serving the files without having a controller for index.html

Currently, react/rails are coupled in that even the index.html must be served from Rails via Webpacker. I would like the Rails APi to be a pure JSON API without any coupling to Webpack.