Non redirect confirm emit continued (Follow up on #288)

[peterpacket]

Follow up for #269

Since PR #288 seems to be inactive, here are the requested changes. It would be very awesome if this PR could be merged, as I need this functionality for my current project.

Original PR content

Follow up for https://github.com/vue-stripe/vue-stripe/issues/269

Tested, works

If the user has passed prop redirect="if_required" and the payment confirmation was successful and the payment method is not forced to redirect then stripe.confirmPayment resolves with a paymentIntent so we sould pass it back up to the caller for consumption:
https://stripe.com/docs/js/payment_intents/confirm_payment?type=pii#confirm_payment_intent-options-redirect

[xpresas]

This is actually needed. I use vue stripe in a modal and no redirect method works for me too. Altho I dont have any response to actually close the modal when payment is done. So $emit confirmed would help me too!

[jofftiquez]

All good! Thank you so much for this.