Introduce renderReactRoot utility
Introduce renderReactRoot utility

Summary: This is a small utility to be able to render a react element without giving it a position somewhere in the react render tree, so that dialogs can be triggered and rendered imperatively for example.

Reviewed By: cekkaewnumchai

Differential Revision: D24021752

fbshipit-source-id: 84633624c63c72a38a1b277207efba75af358a03

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