Allow configuring the webpackHotDevClient with a url

[rzane]

This allows configuring the webpackHotClient with a URL. Currently, the hot client assumes that your frontend code is served from the same window.location, but this is often not true for server-rendered applications using the webpack-dev-server.

This can be configured like so:

entry: [
  `${require.resolve('react-dev-utils/webpackHotDevClient')}?http://0.0.0.0:4001`,
  'your-entry.js'
]

See:
https://github.com/webpack/webpack-dev-server/blob/544d97bf4bee3853c84abb8690923bf93fda4fab/client/index.js#L22

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[gaearon]

Thanks for the PR but I don't think we'll merge this. Mostly because this toolkit is not meant for server-rendered apps in the first place, and even if we fix this, we might make incompatible changes later on. It will be also easier for us to break by accident.

I think your best bet might be to fork this code. Sorry!