[Feature] tabindex attribute on the button

[mandicOfisl]

🚀 Feature Proposal

tabindex attribute for the PayPal button.

Motivation

Very often the visual and HTML order of elements on the page do not match. It could be something as simple as reordering the elements with CSS, or we just want to make a more meaningful tabbing order.
Current implementation offers the role="link" element with the tabindex="0", and it can't be changed even with JS because it's in an <iframe> and it throws a Cross-Origin error.

Example

The usage would be just adding another attribute to the <PayPalButtons> component:

<PayPalButtons createOrder={onCreatePayPalOrder} onApprove={onPayPalApprove} tabindex="3" />

or, for non-React way:

window.paypal.Buttons({ style: { label: "paypal", }, message: { amount: 100, }, tabindex: "3", ...