Update noParse docs

[jakub-g]

1. Warn about [\\/] for portability (/ does not match on Windows)
2. Document noParse x require.

I had an issue like described with 3rd-party lib (webpack 4 was expanding require('os'), require('http') with shims).

An alternative way to prevent expansion of require-s would be defining externals, one by one, but I think noParse is a better solution - I just tell webpack to bundle the file as-is, instead of going through all the code and all those requires.

externals: {
    os: 'var {}',
    http: 'var {}',
    https: 'var {}',
},

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/webpack-docs/webpack-js-org/DTDQXG3UvFbUuzitWWnjEThpB2A6
✅ Preview: https://webpack-js-org-git-fork-jakub-g-patch-4-webpack-docs.vercel.app

[chenxsan]

Can you share the 3rd-party lib you mentioned so I can check? In addition, I noticed you mentioned webpack 4, are those changes for webpack 4 only? We have a https://github.com/webpack/webpack.js.org/tree/webpack-4 branch for webpack 4 documentation, and the master branch is kept for webpack 5.

[EugeneHlushko]

Suggested change

	For example, when building a project for browser target, and using a third-party library that was prebuilt as a dual browser/nodejs lib, and requires some nodejs built-ins, like `require('os')`.
	For example, when building a project for `'browser'` [target](/configuration/target/) and using a third-party library that was prebuilt for both browser and Node.js and it requires Node.js built-ins e.g. `require('os')`.

[EugeneHlushko]

Suggested change

	`noParse` can be also used as a way to deliberately prevent expansion of all `import`, `require`, `define` etc. calls, if you're sure those calls are unreachable at runtime.
	`noParse` can be also used as a way to deliberately prevent expansion of all `import`, `require`, `define` etc. calls for cases when those calls are unreachable at runtime.

[EugeneHlushko]

Suggested change

	Note the need to use `[\\/]` in regex to match `\` on Windows and `/` on Mac/Linux.
	T> You may need to use `[\\/]` in regex to match `\` on Windows and `/` on Mac/Linux.