The following set of components will challenge your knowledge of propTypes and
defaultProps. Alter each component in src/components/ to have the correct
propTypes, and if there's a reasonable place to, add defaultProps. For objects,
do not rely on just PropTypes.object, use PropTypes.shape to define all of
the properties that you know of for the object. If having a property is required
for it to function, or won't look right without it, use .isRequired
When you've fixed them all, open a pull request with your changes.