Add 'How to build driver with phantomjs-prebuilt' (#2086)

Author: vtange

javascript/node/selenium-webdriver/phantomjs.js

@@ -15,6 +15,28 @@
 // specific language governing permissions and limitations
 // under the License.
 
+/**
+ * @fileoverview Defines a {@linkplain Driver WebDriver} client for the PhantomJS
+ * web browser. By default, it is expected that the PhantomJS executable can be located on your [PATH](https://en.wikipedia.org/wiki/PATH_(variable))
+ * 
+ *  __Using a Custom PhantomJS Binary__
+ * 
+ * If you have PhantomJS.exe placed somewhere other than the root of your working directory,
+ * you can build a custom Capability and attach the executable's location to the Capability
+ * 
+ * For example, if you're using the [phantomjs-prebuilt](https://www.npmjs.com/package/phantomjs-prebuilt) module from npm:
+ * 
+ *     //setup custom phantomJS capability
+ *     var phantomjs_exe = require('phantomjs-prebuilt').path;
+ *     var customPhantom = selenium.Capabilities.phantomjs();
+ *     customPhantom.set("phantomjs.binary.path", phantomjs_exe);
+ *     //build custom phantomJS driver
+ *     var driver = new selenium.Builder().
+ *            withCapabilities(customPhantom).
+ *            build();
+ *
+ */
+ 
 'use strict';
 
 const fs = require('fs');