[fix] Reintroduce BackHandler with console.error

This API will be removed in a future version.

Author: necolas

packages/babel-plugin-react-native-web/src/moduleMap.js

@@ -7,6 +7,7 @@ module.exports = {
   AppRegistry: true,
   AppState: true,
   Appearance: true,
+  BackHandler: true,
   Button: true,
   CheckBox: true,
   Clipboard: true,

packages/react-native-web/src/exports/BackHandler/index.js

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Nicolas Gallagher.
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+function emptyFunction() {}
+
+const BackHandler = {
+  exitApp: emptyFunction,
+  addEventListener(): {| remove: () => void |} {
+    console.error(
+      'BackHandler is not supported on web and should not be used.'
+    );
+    return {
+      remove: emptyFunction
+    };
+  },
+  removeEventListener: emptyFunction
+};
+
+export default BackHandler;

packages/react-native-web/src/index.js

@@ -13,6 +13,7 @@ export { default as Animated } from './exports/Animated';
 export { default as Appearance } from './exports/Appearance';
 export { default as AppRegistry } from './exports/AppRegistry';
 export { default as AppState } from './exports/AppState';
+export { default as BackHandler } from './exports/BackHandler';
 export { default as Clipboard } from './exports/Clipboard';
 export { default as Dimensions } from './exports/Dimensions';
 export { default as Easing } from './exports/Easing';