feat: add attachments method

src/BluescaleMailTemplate.php

@@ -144,6 +144,16 @@ class BluescaleMailTemplate implements \JsonSerializable
     }
 
     /**
+     * @param array $attachments
+     * @return BluescaleMailTemplate
+     */
+    public function attachments(array $attachments): BluescaleMailTemplate
+    {
+        $this->attachments = $attachments;
+        return $this;
+    }
+
+    /**
      * @param string $key
      * @param string $value
      * @return BluescaleMailTemplate