Add "New Window" endpoint from W3C spec

Author: robocoder

README.md

@@ -3,7 +3,7 @@ WebDriver for Selenium 2
 This WebDriver client implementation is based on Facebook's [php-webdriver](https://github.com/facebook/php-webdriver/) project by Justin Bishop.
 
 Distinguishing features:
-* Up-to-date with [W3C Candidate Recommendation 08 January 2018](https://w3c.github.io/webdriver/webdriver-spec.html)
+* Up-to-date with [WebDriver: W3C Living Document 31 December 2019](https://w3c.github.io/webdriver/)
 * Up-to-date with [Selenium 2 JSON Wire Protocol](https://github.com/SeleniumHQ/selenium/wiki/JsonWireProtocol) (including WebDriver commands yet to be documented).
 * In the *master* branch, class names and file organization follow PSR-0 conventions for php 5.3+ namespaces.
 * Coding style follows PSR-1, PSR-2, and Symfony2 conventions.

lib/WebDriver/Window.php

@@ -65,4 +65,16 @@ public function getHandle()
             ? $result['value'][self::WEBDRIVER_WINDOW_ID]
             : $result['value'];
     }
+
+    /**
+     * New window: /session/:sessionId/window/new (POST)
+     *
+     * @return \WebDriver\Session
+     */
+    public function focusWindow($name)
+    {
+        $this->curl('POST', '/new');
+
+        return $this;
+    }
 }