export default {
  input: `src/${libraryName}.ts`,
  output: [
    { file: pkg.main, name: camelCase(libraryName), format: 'cjs', sourcemap: true },
    { file: pkg.module, format: 'es', sourcemap: true },
  ],

  ....
}

var x = require('libname').X
console.log(x) // This is undefined

exports.X = X;

module.exports.X = X;

console.log(require('libname')

export default {
  ...
  output: [
      { file: pkg.main, name: camelCase(libraryName), format: 'cjs',
        sourcemap: true,
        outro: 'module.exports = Object.assign({}, module.exports, exports)'
      }
  ]
  ...
}