[Bug] - Disable multiclick on refund

[dan-payplug]

SyliusRefundPlugin version affected: All

Description
Prevent multi-click for refund button

Steps to reproduce

• Sign in to BO
• Go on order detail paid successfully
• Refund the customer for the order
• Select the items to refund
• Multi click on Refund button quickly

Result observed

• There are several error/success messages regarding the number of click on the Refund button

Possible Solution

• The button is disabled after hitting the first click to prevent multi error/success messages

[GSadee]

Hi @dan-payplug, thank you for reporting the issue, indeed it should be secured, probably not only in this place. Would you like to open a PR with such a fix?