Add Support Ukraine banner
Add Support Ukraine banner

Summary:
Inspired by https://github.com/facebook/react-native-website/pull/2988

Changelog: Add Support Ukraine banner to website

Reviewed By: antonk52, aigoncharov

Differential Revision: D34627820

fbshipit-source-id: 61f69984451c504eca9a6f5e55f30d968344129e

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