Plugins that write on stdout

[GuillaumeCisco]

Hello there,

I think this is important to note that the json file generated as described in the README can contain stdout lines making it nit a json file.

For example, I have some plugins like SWPrecacheWebpackPlugin, AutoDllPlugin that write on the stdout outout, so the generated file is not a true json file.

Maybe we should handle the creation of the json file by stripping the written lines at the beginning of the file or find another way to generate a json file correctly.

Right now, we should add a troubleshooting section in the README for warning users about it before they say "it does not work"

[d4rkr00t]

Hi :) I'll try to figure something out :)