Summary:
I wanted to configure the RN dev menu without having to write native code. This is pretty useful in a greenfield app since it avoids having to write a custom native module for both platforms (and might enable the feature for expo too).
This ended up a bit more involved than planned since callbacks can only be called once. I needed to convert the `DevSettings` module to a `NativeEventEmitter` and use events when buttons are clicked. This means creating a JS wrapper for it. Currently it does not export all methods, they can be added in follow ups as needed.
## Changelog
[General] [Added] - Export the DevSettings module, add `addMenuItem` method
Pull Request resolved: https://github.com/facebook/react-native/pull/25848
Test Plan:
Tested in an app using the following code.
```js
if (__DEV__) {
DevSettings.addMenuItem('Show Dev Screen', () => {
dispatchNavigationAction(
NavigationActions.navigate({
routeName: 'dev',
}),
);
});
}
```
Added an example in RN tester
Differential Revision: D17394916
Pulled By: cpojer
fbshipit-source-id: f9d2c548b09821c594189d1436a27b97cf5a5737
Summary: See previous diff in this stack
Reviewed By: motiz88
Differential Revision: D17156649
fbshipit-source-id: 12bdba248481258b9c6ca001472a41ca19fb4b6f
Janic Duplessis
Christoph Nakazawa
Logan Daniels
Kevin Gozali
Petr Nikolaev
Jarvis Luong
