document for specifying the buildHttp.proxy for HttpUrlPlugin

[aleen42]

For webpack/webpack#15354

closes #5994

• Read and sign the CLA. PRs that haven't signed it won't be accepted.
• Make sure your PR complies with the writer's guide.
• Review the diff carefully as sometimes this can reveal issues.
• Do not abandon your Pull Request: Stale Pull Requests.
• Remove these instructions from your PR as they are for your eyes only.

[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/89CFGd32f8MsmdSmoWGvhforrQoC
✅ Preview: https://webpack-js-org-git-fork-aleen42-proxy-webpack-docs.vercel.app

[chenxsan]

Hi, thanks for your patience. I've left some suggestions, let me know what you think.

[chenxsan]

Suggested change

	By default webpack would try to use the `http_proxy` environment variable to specify the proxy server for remote resources. Besides, you can define the proxy server by setting the `proxy` option.
	By default webpack would imply the proxy server to use for fetching remote resources from the `http_proxy` environment variable. However, you can also specify one through the `proxy` option.

Should it be https_proxy?

[aleen42]

Confirmed that using http_proxy.

[snitin315]

Is this case sensitive? or both http_proxy/HTTP_PROXY works?

[aleen42]

both works, how about

- By default webpack would imply the proxy server to use for fetching remote resources from the `http_proxy` environment variable. However, you can also specify one through the `proxy` option.
+ By default, Webpack would imply the proxy server to use for fetching remote resources from the `http_proxy` (case insensitive) environment variable. However, you can also specify one through the `proxy` option.

[snitin315]

Works for me. /cc @chenxsan