Add opts for specify location of node_modules

[DrSensor]

I have a case when I need to specify the directory of node_modules because using https://yarnpkg.com/blog/2017/08/02/introducing-workspaces/ . I have separate client and server folder with separate package.json and I notice this package don't have an option to specifying the directory of src node_modules.

This is what I want to achieve.

copyNodeModule(path.resolve(__dirname, '../server'), config.build.assetsRoot, {
      srcDir: __dirname,
      devDependencies: false
    }, (err, results) => {