Update composer.json for PHP 7.2

vendor/psr/http-client/src/ClientInterface.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Psr\Http\Client;
+
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+
+interface ClientInterface
+{
+    /**
+     * Sends a PSR-7 request and returns a PSR-7 response.
+     *
+     * @param RequestInterface $request
+     *
+     * @return ResponseInterface
+     *
+     * @throws \Psr\Http\Client\ClientExceptionInterface If an error happens while processing the request.
+     */
+    public function sendRequest(RequestInterface $request): ResponseInterface;
+}