Add method download

Download a document sent to the bot

\Mateodioev\Bots\Telegram\Api->download($file_path, $destination, $timeout)

$file_path: Get with Api->request('getFile', ['file_id' => $unique_file_id]);
$destination: Name of the document where the file will be saved
$timeout: Request timeout

Full Changelog: v1.2...v1.2.1