Expected behavior

Sending css property should export CSS file.

    vue({
      css: './build/assets/css/bundle.css'
    }),

Actual behavior

No file is exported.

Steps to reproduce the behavior

Upgraded 'rollup-plugin-vue' from 2.5 to 4.0.0, with no changes to 'rollup.config.js'. The CSS files is no longer exported.

Reverting the plugin back to 2.5 the problem is solved.