content: import React from 'react'
  import PropTypes from 'prop-types'
  
  // Dumb counter component --- As it has no business logic.
  const Counter = (props) => (
    <div>
      <h1>{props.value}</h1>
      <button className="btn btn-primary" onClick={props.onIncrement}>+</button>
      <button className="btn btn-warning" onClick={props.onDecrement}>-</button>
    </div>
  );
  
  Counter.propTypes = {
    value : PropTypes.number.isRequired,
    onIncrement: PropTypes.func.isRequired,
    onDecrement: PropTypes.func.isRequired,
  };
  
  export default Counter;
  