Add localized accessibility strings to React Core pod (#27995)

Summary:
The accessibility roles and states description strings are not able to be localized on iOS platform. Those strings are exposed to the end users so it should be localized. This PR is to add localized strings as a resource bundle to the React Core Pod so that any React Native app integrating the React Native dependencies using CocoaPods can get the localized accessibility roles and states description.

## Changelog

[iOS] [Added] - Add localized accessibility strings to React Core pod
Pull Request resolved: https://github.com/facebook/react-native/pull/27995

Test Plan: Verified with RNTester app.

Differential Revision: D19975587

Pulled By: PeteTheHeat

fbshipit-source-id: f8eb4e25194f0cd603c98a6221ec87503a2826ed

React-Core.podspec

@@ -44,6 +44,7 @@ Pod::Spec.new do |s|
   s.author                 = "Facebook, Inc. and its affiliates"
   s.platforms              = { :ios => "10.0", :tvos => "10.0" }
   s.source                 = source
+  s.resource_bundle        = { "AccessibilityResources" => ["React/AccessibilityResources/*.lproj"]}
   s.compiler_flags         = folly_compiler_flags + ' ' + boost_compiler_flags
   s.header_dir             = "React"
   s.framework              = "JavaScriptCore"