add docs

Author: cesargb

README.md

@@ -0,0 +1,32 @@
+# Omnipay:: Offline dummy
+
+Omnipay Offline Dummy Gateway for testing
+
+## Instalation
+
+```sh
+composer require descom/omnipay-offline-dummy
+```
+
+## Basic Usage
+
+### Create purchase request
+
+```php
+use Omnipay\Omnipay;
+
+$gateway = Omnipay::create('OfflineDummy');
+
+$gateway->initialize([
+    'url_notify' => 'http://example.com/payment/notify',
+    'url_return' => 'http://example.com/payment/return',
+]);
+
+$request = $gateway->purchase([
+                'amount' => '12.00',
+                'description' => 'Test purchase',
+                'transactionId' => 1,
+            ])->send();
+
+$response->redirect();
+```