getJson method
Make a GET request and return JSON response
Implementation
Future<Map<String, dynamic>> getJson(
  String endpoint, {
  CancelToken? cancelToken,
}) async {
  try {
    final response = await _dio.get(
      endpoint,
      cancelToken: cancelToken,
    );
    if (response.statusCode != 200) {
      throw ProviderError(
        'ElevenLabs API returned status ${response.statusCode}: ${response.data}',
      );
    }
    return response.data as Map<String, dynamic>;
  } on DioException catch (e) {
    throw DioErrorHandler.handleDioError(e, 'ElevenLabs');
  }
}