Add CI workflow (#4054)
Add CI workflow (#4054)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/4054

Build RNW example on Github

Reviewed By: aigoncharov

Differential Revision: D39257309

fbshipit-source-id: dda414c025bfe6720449fe6c3d81fe9fb9373b2a

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