Visual enhancement for BNPL terms presentation in Checkout block

[orcungogus]

In order to better emphasize the WooPayments BNPL terms within the layout structure of the Payment options block, we want to implement a bounding box to differentiate the dynamic offer terms presented within each expanded accordion element.

Figma: 96Xr930vUUS29z5ta3CsD3-fi-407_734

The background color of the bounding box should provide enough contrast for the content shown within the offer terms section.