support dynamic templateFilename of type in RegExp: r'^[a-zA-Z0-9]+[a-zA-Z0-9-]+.arb$'.
template file name can be: intl_en.arb, intl_en_US.arb, app_zh.arb an so on.
Core codes here:
final arbDir = _config['arb-dir'] as String? ?? "lib/l10n";
final templateFilename = _config['template-arb-file'] as String? ?? "app_en.arb";
final source = templateFilename.substring(templateFilename.indexOf(RegExp(r'[-_]')) + 1, templateFilename.indexOf('.arb'));
final name = templateFilename.substring(0, templateFilename.indexOf(RegExp(r'[-_]')));
template file name can be: intl_en.arb, intl_en_US.arb, app_zh.arb an so on.
Core codes here: