Add userInterfaceStyle option to Alert

[luoxuhai]

Support to override Alert interface style to match your app. For example, You want to change the style of the alert.

react-native PR: react/react-native#33553

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[Simek]

Since the 0.69 was shipped and docs for the release has been cut, we can merge those changes in. 🙂

LGTM, nice attention to the details, thank you for the docs PR @luoxuhai! 🙏