add Currency aggregator NAtional Bank of Ukraine with API

Hello

In the new version of the plugin, you can use the hook to add a custom aggregator

Example:

add_filter("woocs_add_custom_rate",function($rate,$default_currency,$current_currency){
    $url = 'https://api.some_bank_test.com/api/info?json&currencies='.$default_currency.'_'.$current_currency; 
    $res = file_get_contents($url);
    if($res AND isset($res['rate'])){
      $rate=$res['rate'];
     }
    return $rate;
},10,3);