Add a Help menuitem (#180)

added a new link on the content.html page and updated the corresponding action in the main.js file
So I tested this via 'ant run', and this line fails because window is not known. What you have to do here is to import another library specifically for window related actions. More information can be found here:

https://developer.mozilla.org/en-US/Add-ons/SDK/Low-Level_APIs/window_utils#open%28uri.2C_options%29

I would also suggest that you test your patch before the next review request.