Add extremely basic WebKit example.
user
```ruby
# Based on http://www.idle-hacking.com/2010/02/webkit-ruby-and-gtk/
$LOAD_PATH.unshift File.join(File.dirname(__FILE__), '..', 'lib')
require 'gir_ffi'

GirFFI.setup :Gtk
GirFFI.setup :WebKit

Gtk.init

win = Gtk::Window.new :toplevel
wv = WebKit::WebView.new
win.add(wv)
win.show_all
wv.open('http://www.google.com/')
GObject.signal_connect(win, "destroy") { Gtk.main_quit }
Gtk.main
```
assistant