Update README.md

Author: mdjastrzebski

README.md

@@ -102,6 +102,7 @@ React Native Testing Library consists of following APIs:
 
 ## Migration Guides
 
+- [Migration to 13.0 (RC)](https://callstack.github.io/react-native-testing-library/13.x-next/docs/migration/v13)
 - [Migration to 12.0](https://callstack.github.io/react-native-testing-library/docs/migration/v12)
 - [Migration to built-in Jest Matchers](https://callstack.github.io/react-native-testing-library/docs/migration/jest-matchers)