• Rollup Version: 2.26.3
• Operating System (or Browser): Chrome
• Node Version (if applicable): v12.16.1
• Link to reproduction (IMPORTANT, read below):

Expected Behavior

 -dist
 --my-faceapi-js-lib.cjs.js
 --my-faceapi-js-lib.esm.js
 --my-faceapi-js-lib.umd.js
 --my-faceapi-js-lib.css

Actual Behavior

I'm writing JS library using rollup-starter-lib as base of my JS library

Before update rollup version, I feel like it's .css file not creating due to tree shaking because of css not used in this JS library itself.

Then, I update rollup version to 2.26.3 from 1.29.0 now it's generate only following two files along with below error. It's seams there is an issue with rollup or postCss plugin.

--my-faceapi-js-lib.umd.js
--my-faceapi-js-lib.css

[!] Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
src/main.css (1:0)

rollup.config.js

import resolve from '@rollup/plugin-node-resolve';
import commonjs from '@rollup/plugin-commonjs';
import pkg from './package.json';
import path from 'path'
import postcss from 'rollup-plugin-postcss'

export default [
	{
		input: 'src/main.js',
		output: {
			name: 'my-faceapi-js-lib',
			file: pkg.browser,
			format: 'umd'
		},
		plugins: [
			postcss({
				minimize: true,
				extensions: ['.css'],
				extract: path.resolve('dist/my-faceapi-js-lib.css'),
			}),
			resolve(), // so Rollup can find `ms`
			commonjs() // so Rollup can convert `ms` to an ES module
		]
	},
	{
		input: 'src/main.js',
		external: ['ms'],
		output: [
			{ file: pkg.main, format: 'cjs' },
			{ file: pkg.module, format: 'es' }
		]
	}
];

main.js

import * as faceapi from "face-api.js";
...
import './main.css';
...
...

Basically there is not usage of main.css within JS library it self. but it's necessary when integrate this library.