Add Account Member Creation (#192)

We can now create account members threough the SDK

src/Endpoints/AccountMembers.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Cloudflare\API\Endpoints;
+
+use Cloudflare\API\Adapter\Adapter;
+use Cloudflare\API\Traits\BodyAccessorTrait;
+
+class AccountMembers implements API
+{
+    use BodyAccessorTrait;
+
+    /**
+     * @var Adapter
+     */
+    private $adapter;
+
+    public function __construct(Adapter $adapter)
+    {
+        $this->adapter = $adapter;
+    }
+
+    public function addAccountMember(string $accountId, string $email, array $roles): \stdClass
+    {
+        $options = [
+            'email' => $email,
+            'roles' => $roles,
+        ];
+
+        $account    = $this->adapter->post('accounts/' . $accountId . '/members', $options);
+        $this->body = json_decode($account->getBody());
+
+        return $this->body->result;
+    }
+}