Add warning that CameraRoll has been moved to RNC (#23733)

Summary:
Adds a moved warning to the CameraRoll import directing people to the react-native-community/cameraroll package.

[Lean Core] [Warning] add warning that CameraRoll has been moved to RNC
Pull Request resolved: https://github.com/facebook/react-native/pull/23733

Differential Revision: D14298485

Pulled By: cpojer

fbshipit-source-id: cf03660c604a7337f234da107d7069c0ccf99f36

Libraries/react-native/react-native-implementation.js

@@ -213,6 +213,12 @@ module.exports = {
     return require('BackHandler');
   },
   get CameraRoll() {
+    warnOnce(
+      'cameraroll-moved',
+      'CameraRoll has been extracted from react-native core and will be removed in a future release. ' +
+        "It can now be installed and imported from '@react-native-community/cameraroll' instead of 'react-native'. " +
+        'See https://github.com/react-native-community/react-native-cameraroll',
+    );
     return require('CameraRoll');
   },
   get Clipboard() {