Add the possibility to keep the js class names in the production build

[svenliebig]

I added an environment variable to prevent the terser plugin from minifying js class names in the production build.

The variable is: KEEP_CLASS_NAMES - i added an example in the documentation, beneath the production-build documentation.

There is no major change, the production build will be equal to the production build before this pull request, if there is no environment variable set.

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[stale]

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[svenliebig]

Is there any possibility to get this merged?

[keblodev]

so why no one looked at this? not even a feedback comment?
cuz this is literally what's happening right now with my app and me forced to use libraries that use material-ui with it's well known awesome way of doing markup and styles making it impossible to override if the library does not provides any means.

this ENV variable is exactly what my projects needs right now.

[RichardSto]

For everyone who might be searching for a solution to keep the classnames in build here is one:

NODE_ENV=production ./node_modules/.bin/react-scripts build --profile

In "node_modules/react-scripts/webpack.config.js" this affects isEnvProductionProfile in said file,

module.exports = function (webpackEnv) {
  const isEnvDevelopment = webpackEnv === 'development';
  const isEnvProduction = webpackEnv === 'production';

  // Variable used for enabling profiling in Production
  // passed into alias object. Uses a flag if passed into the build command
  const isEnvProductionProfile =
    isEnvProduction && process.argv.includes('--profile');

which will lead to

 // Added for profiling in devtools
 keep_classnames: isEnvProductionProfile,

keep_classnames being true and as the name points out, classnames will be kept.

Props for coming up this solution go to @tstec-polypoly.

[Timer]

Just leaving this review since I saw it in my pending requests! Best of luck with the PR! Seems to be a GitHub bug since I no longer have rights.