work.suroh.tk/node_modules/acorn/rollup/config.main.js

import buble from 'rollup-plugin-buble';

export default {
	entry: 'src/index.js',
	moduleName: 'acorn',
	plugins: [ buble() ],
	targets: [
		{ dest: 'dist/acorn.js', format: 'umd' },
		{ dest: 'dist/acorn.es.js', format: 'es' }
	]
};