[react-scripts] Do not lint *.bs.js files, generated by BuckleScript

Created by: emmenko

Summary

This PR introduces a small change in the eslint rule of webpack.config to exclude files ending with the suffix *.bs.js (which are compiled files generated by BuckleScript).

NOTE: I'm no RegEx expert, so if someone has a better suggestion about the test rule feel free to leave a comment 🙏

Background

When working on a React project which includes fully or partially ReasonML, you need BuckleScript to generate the compiled JS sources. When you have the in-source option active you will get the compiled JS sources (*.bs.js) next to the Reason source file. Those files will therefore "live" inside the src folder, causing eslint to print some warnings:

This is a bit annoying and can simply be "solved" by telling eslint to ignore those files.

Wait, ReasonML? What about reason-scripts?

As you might know, there is a package called reason-scripts which is basically a "clone" of react-scripts, with some things adapted to compile Reason files out of the box (e.g. entry point index.re instead of index.js).

However, as I pointed out in this issue, I don't think it's necessary to have reason-scripts in the first place. @rrdelaney also pointed out (correctly if I'm wrong) that bs-loader should not be included in the package anymore. In fact, you can run the BuckleScript compiler in watch mode as a parallel process, next to react-scripts start. This way you don't need the loader at all and you can simply use the "normal" react-scripts package.

"scripts": {
  "start": "npm-run-all --parallel start:bsb start:app",
  "start:app": "react-scripts start",
  "start:bsb": "bsb -make-world -w",
}

Anyway, this is another story...

Btw, this change will need to be made in reason-scripts as well.

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Hopefully this gives you enough background/context to understand this change. I'm open to any feedback/suggestion.

Thanks 🙏