docs: add GH button in support of Ukraine (#204)
docs: add GH button in support of Ukraine (#204)

Summary:
Our mission at Meta Open Source is to empower communities through open source, and we believe that it means building a welcoming and safe environment for all. As a part of this work, we are adding this banner in support for Ukraine during this crisis.

Pull Request resolved: https://github.com/facebook/wangle/pull/204

Reviewed By: lnicco

Differential Revision: D34630963

Pulled By: dmitryvinn-fb

fbshipit-source-id: 839f6913f65ab0692d1d143d0a5d2d523f0611dc

facebook/wangle,facebook/wangle,facebook/wangle