微信红包增加find查询

用法
`
$wechat->find('商户订单号mch_billno', 'redpack');
`

src/Gateways/Wechat/RedpackGateway.php

@@ -49,6 +49,22 @@ class RedpackGateway extends Gateway
         );
     }
 
+    /**
+     * Find.
+     *
+     * @author yansongda <me@yansongda.cn>
+     *
+     * @param $billno
+     */
+    public function find($billno): array
+    {
+        return [
+            'endpoint' => 'mmpaymkttransfers/gethbinfo',
+            'order' => ['mch_billno' => $billno, 'bill_type' => 'MCHT'],
+            'cert' => true,
+        ];
+    }
+    
     /**
      * Get trade type config.
      *