process variable is undefined when use DefinePlugin

I wrote about this bug in [another issue](https://github.com/javascript-obfuscator/javascript-obfuscator/issues/863), but it is already closed, it would probably be more correct to make a separate issue in a more suitable repository for this.

I made a [minimal example](https://github.com/Katarn/obfuscator-process-bug).

Just run `npm ci && npm run build`. After that, in the `dist` directory, you will see the `main.js` file. Open it in a code editor and you will see something like:

```js
....shift())}}(n),process[r(309)][r(311)]&&console[r(302)](r(311))})();...
```

Of course, the `process` variable is `undefined`. Moreover, it should not be in the code, it should either be replaced with `true` (according to [this line](https://github.com/Katarn/obfuscator-process-bug/blob/master/webpack.config.js#L22)), or, with "smart optimization", the `if (...)` check block should not exist at all, since it will always be executed.

Then you can uncomment these [two lines](https://github.com/Katarn/obfuscator-process-bug/blob/5edcd56c5f2f18b6068e8459f7be075fc9691bb5/webpack.config.js#L14-L15) (not necessarily at the same time, you can uncomment them separately) and see how the code is generated in the `main.js` file.

Inizia dal webpack.config.js dell'esempio minimale, in particolare dalla configurazione di DefinePlugin intorno alle righe 14-15 e 22, quindi esegui npm ci && npm run build. Esamina dist/main.js con le opzioni abilitate e confronta se process viene sostituito o eliminato dall'ottimizzazione come previsto.

Scritto dal modello di indicizzazione a partire dal testo della issue.