content: import React from 'react'
  import PropTypes from 'prop-types'
  
  export const Counter = ({ counter, increment, doubleAsync }) => (
    <div style={{ margin: '0 auto' }} >
      <h2>Counter: {counter}</h2>
      <button className='btn btn-primary' onClick={increment}>
        Increment
      </button>
      {' '}
      <button className='btn btn-secondary' onClick={doubleAsync}>
        Double (Async)
      </button>
    </div>
  )
  Counter.propTypes = {
    counter: PropTypes.number.isRequired,
    increment: PropTypes.func.isRequired,
    doubleAsync: PropTypes.func.isRequired,
  }
  
  export default Counter
  