https://developer.apple.com/documentation/apple_pay_on_the_web/displaying_apple_pay_buttons_using_css claims that the `-apple-pay-button-type` CSS property accepts the `continue` and `pay` values for specific button types, but local testing indicates that we fall back to the `plain` button type when these properties are used.
rdar://116820183
Pull request: https://github.com/WebKit/WebKit/pull/20495
Closing this bug because we've decided not to implement these two button types in `-apple-pay-button-type` CSS. Support for them exists in the Apple Pay JS SDK instead: https://developer.apple.com/documentation/apple_pay_on_the_web/displaying_apple_pay_buttons_using_javascript