Update ReponseInterface documentation

src/Response/ResponseInterface.php

@@ -1,11 +1,33 @@
 <?php
+
 namespace ByJG\ApiTools\Response;
 
+use Psr\Http\Message\StreamInterface;
+
+/**
+ * Adds an ability to return response of any kind without PSR dependency.
+ */
 interface ResponseInterface
 {
+    /**
+     * @return string[][] Returns an associative array of the message's headers. Each
+     *     key MUST be a header name, and each value MUST be an array of strings
+     *     for that header.
+     */
     public function getHeaders();
 
+    /**
+     * The status code is a 3-digit integer result code of the server's attempt
+     * to understand and satisfy the request.
+     *
+     * @return int Status code.
+     */
     public function getStatusCode();
 
+    /**
+     * Gets the body of the message.
+     *
+     * @return StreamInterface|string Returns the body as a stream.
+     */
     public function getBody();
 }