Allow intl to support multiple translations per locale.

It keeps an already loaded translation if the intl message lookup mechanism was initialized with a CompositeMessageLookup subclass (as intl_translation and intl_utils do).

Usage

Call initializeMultipleTranslations() before loading another translation for the same locale.

You can do this before loading any translation, for example, in the main function:

import 'package:intl_multiple_translations/intl_multiple_translations.dart';

Future<void> main() async {
  initializeMultipleTranslations();
  await initializeMessages('es');
  await initializeMoreMessages('es');
  ...
}

or before loading additional translations, for example, in a package:

import 'package:intl_multiple_translations/intl_multiple_translations.dart';

Future<bool> initializePackageMessages(String localeName) {
  initializeMultipleTranslations();
  return initializeMessages(localeName);
}