Add Flow to @react-native/polyfills entry point (#44477)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44477

Changelog: [Internal]

TSIA

Reviewed By: huntie

Differential Revision: D57091620

fbshipit-source-id: 54fd105069ba0a34b9ab5bd12295e4e9641492a3

packages/metro-config/src/index.flow.js

@@ -58,7 +58,6 @@ export function getDefaultConfig(projectRoot: string): ConfigT {
       getModulesRunBeforeMainModule: () => [
         require.resolve('react-native/Libraries/Core/InitializeCore'),
       ],
-      // $FlowFixMe[untyped-import]
       getPolyfills: () => require('@react-native/js-polyfills')(),
       isThirdPartyModule({path: modulePath}: $ReadOnly<{path: string, ...}>) {
         return (

packages/polyfills/index.js

@@ -4,12 +4,13 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
+ * @flow strict-local
  * @format
  */
 
 'use strict';
 
-module.exports = () => [
+module.exports = () /*: Array<string> */ => [
   require.resolve('./console.js'),
   require.resolve('./error-guard.js'),
 ];

packages/react-native/rn-get-polyfills.js

@@ -4,6 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
+ * @flow strict-local
  * @format
  */