initial usage example added

Author: Vitexus

Examples/balance.php

@@ -0,0 +1,17 @@
+<?php
+
+require_once(dirname(__DIR__) . '/vendor/autoload.php');
+
+$apiInstance = new \SpojeNET\Csas\Accounts\DefaultApi(
+        // If you want use custom http client, pass your client which implements `GuzzleHttp\ClientInterface`.
+        // This is optional, `GuzzleHttp\Client` will be used as default.
+        new GuzzleHttp\Client()
+);
+$id = 'id_example'; // string | Opaque system ID of the account
+
+try {
+    $result = $apiInstance->getAccountBalance($id);
+    print_r($result);
+} catch (Exception $e) {
+    echo 'Exception when calling DefaultApi->getAccountBalance: ', $e->getMessage(), PHP_EOL;
+}