Set module resolution based on baseUrl in jsconfig/tsconfig.json

Created by: rovansteen

Based on this thread on Twitter here is a PR to kickstart development/discussion on supporting absolute paths in Typescript via NODE_PATH so they work consistently between JS & TS.

Updated: Based on the discussion here: https://github.com/facebook/create-react-app/issues/5645#issuecomment-451170386 This attempts to unify the configuration by reading baseUrl from jsconfig.json / tsconfig.json.

🚧 This PR is still in progress

To do:

• Add tests
• Make sure paths are valid TypeScript
• Add deprecation message to react-scripts start
• Add documentation