Add props to control Icon and clickEvent

[stonehz]

I've added 2 extra props alongside with tests and an update to the readme file.

The thought process

showIcon ➡️ Since we are passing children, it makes sense to also control Icon visibility and allow Children to pass another icon or a more advanced component.

handleClick ➡️ The idea behind this was aimting to extend the click event so the user has the ability to attach tracking or some access logic to the button.