This folder contains libs that aren't meant to be modified in the project.
Example: I've the following problem at build with @fnando/sparkline:
Failed to minify the code from this file:
./node_modules/@fnando/sparkline/src/sparkline.js:6
The package.json file is like this:
"main": "dist/sparkline.js",
"module": "src/sparkline.js",
The reason seams to be that the webpack config of create-react-app is meant to use the ESModule version of a package when possible, but since it is in the node_modules, it doesn't transpiles them.
So it won't transpile the spread operator (l6) nor export as a CommonJS module for Babel.
Still in progress ...