Allow to use function as publicPath

[nkbt]

Webpack has added support to use use function as publicPath quite a while ago

Commit: https://github.com/webpack/webpack/commit/fb4070442a3c0feb115dbb9229ccd0dc1458b30d

At this moment publicPath in webpack-manifest-plugin is assumed to be a string, so when I am using function as webpack.output.publicPath option, I ended up with something like this in my manifest.json:

{
  "bootstrap.js": "url => `/static/${url}`bootstrap.js",
  "main.css": "url => `/static/${url}`main.css"
}

Here is exactly why it is happening:

    var publicPath = this.opts.publicPath != null ? this.opts.publicPath : compilation.options.output.publicPath;

  // ...
  // then further in the code function is implicitly casted to String

    if (publicPath) {
      files = files.map(function(file) {
        file.path = publicPath + file.path;
        //                ^^^^^^^^^^^^^^^ here function publicPath is converted to string
        return file;
      }.bind(this));
    }

[towry]

I assume this will solve the multiple publicPath problem.

[shellscape]

Hey all! I've taken over maintenance of the plugin and am doing some housecleaning. For Issues over a year old without a reproduction, we're going to go the route of closing them first. However, they're not dead! If the issue is still pending and still a problem, please reply with a reproduction and we'll reopen post-haste.

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