Make timeout customizable

[obuchmann]

I'm currently working on a sync tool that uses the api. Due to the high number of users in my system the timeout excedes sometimes.

You should be able to set the timeout when creating a new Client instance.

e.g.

use ZammadAPIClient\Client;
$client = new Client([
    'url'           => 'https://myzammad.com', // URL to your Zammad installation
    'username'      => 'myuser@myzammad.com',  // Username to use for authentication
    'password'      => 'mypassword',           // Password to use for authentication
    'timeout'       => 15,                // Sets timeout to 15 seconds
]);