Summary:
When you write platform-specific code using [file extensions](https://facebook.github.io/react-native/docs/platform-specific-code#platform-specific-extensions), you can specify `.ios.js`, `.android.js`, or the catch-all `.native.js` when you are sharing code with a web project.
This `native` shortcut is missing for the `Platform.select` method, and this PR is adding support for that.
## Changelog
[General] [Added] - Platform.select now supports native as an option.
Pull Request resolved: https://github.com/facebook/react-native/pull/26966
Test Plan: Added relevant passing unit tests for Platform module.
Differential Revision: D18323670
Pulled By: cpojer
fbshipit-source-id: 7524c1914beab4f86041dcf8e60875380ebf7e02