[react-native] Add module DevSettings (#43679)

* feat: add dev settings to react-native

* test: add test calls for dev settings

* fix: remove trailing whitespace

types/react-native/index.d.ts

@@ -35,6 +35,7 @@
 //                 Mohamed Shaban <https://github.com/drmas>
 //                 André Krüger <https://github.com/akrger>
 //                 Jérémy Barbet <https://github.com/jeremybarbet>
+//                 Christian Ost <https://github.com/ca057>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.8
 
@@ -8913,6 +8914,28 @@ export interface KeyboardStatic extends NativeEventEmitter {
     addListener(eventType: KeyboardEventName, listener: KeyboardEventListener): EmitterSubscription;
 }
 
+/**
+ * The DevSettings module exposes methods for customizing settings for developers in development.
+ */
+export interface DevSettingsStatic extends NativeEventEmitter {
+    /**
+     * Adds a custom menu item to the developer menu.
+     *
+     * @param title - The title of the menu item. Is internally used as id and should therefore be unique.
+     * @param handler - The callback invoked when pressing the menu item.
+     */
+    addMenuItem(title: string, handler: () => any): void;
+
+    /**
+     * Reload the application.
+     *
+     * @param reason
+     */
+    reload(reason?: string): void;
+}
+
+export const DevSettings: DevSettingsStatic;
+
 //////////////////////////////////////////////////////////////////////////
 //
 //  R E - E X P O R T S

types/react-native/test/index.tsx

@@ -96,6 +96,7 @@ import {
     HostComponent,
     Appearance,
     useColorScheme,
+    DevSettings,
 } from 'react-native';
 
 declare module 'react-native' {
@@ -1085,3 +1086,10 @@ const DarkMode = () => {
 
     return <Text>Is dark mode enabled? {isDarkMode}</Text>;
 };
+
+// DevSettings
+DevSettings.addMenuItem('alert', () => {
+    Alert.alert('alert');
+});
+DevSettings.reload();
+DevSettings.reload('reload with reason');