Upgrade to emotion v10

Summary: React 16 is not compatible with react-emotion 9 (it prints warnings, see also https://github.com/emotion-js/emotion/issues/644). So we should upgrade to 10.

Reviewed By: mweststrate

Differential Revision: D18905889

fbshipit-source-id: c00d2dbbadb1c08544632cb9bfcd63f2b1818a25

src/index.tsx

@@ -7,7 +7,8 @@
  * @format
  */
 
-export {default as styled, keyframes} from 'react-emotion';
+export {default as styled} from '@emotion/styled';
+export {keyframes} from 'emotion';
 export * from './ui/index';
 export {getStringFromErrorLike, textContent} from './utils/index';
 export {serialize, deserialize} from './utils/serialization';