This allows the plugin to be configured to run on an allowlist, rather
than compiling all files helping with an incremental rollout plan.
The sources option takes both an array of path strings or a function
to be flexible.
For now I've left this be optional but we can make it required.
ghstack-source-id: 282a33dc8d08d47f699894692e0fcc813dff5b77
Pull Request resolved: https://github.com/facebook/react-forget/pull/2855