.css file not added into distribution in JS only library

[ghost]

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

It has main.js file & main.css file, There is no html file.
main.js file is all about DOM manipulation, main.css file is necessary in implementation steps, to easily integrate this JS library, rather giving an instruction to user.

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

Current Distribution

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

Expected Distribution

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

copy main.css file into dist folder not expecting since it's not minifying.

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: 'howLongUntilLunch',
			file: pkg.browser,
			format: 'umd'
		},
		plugins: [
                         postcss({
				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
		]
	}
];

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.

[pawelkrystkiewicz]

@chanukagzone how did you solve this? I'm facing the same issue