Improvement: add a startOnLoad argument to useCounter

[yashshah1]

Currently, when using useCountdown, the caller code also needs to do a startCountdown on page load something like:

const Component = () => {
	const [secondsRemaining, { startCountdown, resetCountdown }] = useCountdown({countStart: 60});

	useEffect(() => startCountdown(), []);

	return <>You have {secondsRemaining}s left</>;
}

Suggestion

const Component = () => {
	const [secondsRemaining, { startCountdown, resetCountdown }] = useCountdown({countStart: 60, startDefault: true});

	return <>You have {secondsRemaining}s left</>;
}

startDefault (name up to debate) starts the countdown by default once the hook is called.