[react-centra-checkout]: support parameter `actionHandler` for `submitPayment`

[adamsoderstrom]

Currently there's no way to do a custom action handler when using the submitPayment hook.
Therefore, we need to do optimistic logic (either do actions on "order confirmation" page or before calling submitPayment).

We should be able to opt-out of the default action handler, so we can validate that the payment was successful, trigger other logic and then redirect (or other).

accelerator/packages/react-centra-checkout/src/Context/index.tsx

Lines 414 to 437 in 995809e

	// handle redirecting here
	switch (response.action) {
	case 'redirect':
	if (response.url) {
	window.location.href = response.url
	}
	break
	case 'success':
	// according to Centra docs – if action === 'success', user should be forwarded directly to the receipt page
	window.location.href = `${receiptPage}/${response.token}`
	break
	case 'javascript':
	if (response.code) {
	const script = document.createElement('script')
	const text = document.createTextNode(response.code)
	script.appendChild(text)
	document.body.appendChild(script)
	}
	break
	default:
	return response
	}
	return response
	},