Allow to pass used hook to plugin

[DiskoPete]

Hi

I run into a problem to use this plugin in conjunction with the filemanager-webpack-plugin plugin.

The problem occurred because the filemanager plugin was executed on the 'afterEmit' hook whilst replace-in-file executes on the 'done' hook.

Therefore the files were copied before the content was replaced.

To fix this I introduced a new hook property as a configuration option.
It allows to specify which compiler hook the plugin should use and defaults to 'done'.

I had to restructure the code a bit and move the callback inside the forEach loop to allow a different 'hook' value per option.

Regards
Peter

Sidenote
I removed this condition because I didn't need it for my purpose but if you think this changes makes sense to be merged, I am happy to add it back.

if (statsData.hasErrors()) {
    return
}